diff --git a/FrameBuffer.cpp b/FrameBuffer.cpp
index b1cb0b4..0635e58 100644
--- a/FrameBuffer.cpp
+++ b/FrameBuffer.cpp
@@ -65,6 +65,8 @@ void FrameBuffer::init()
                                 use_alpha_ ? GL_RGBA8 : GL_RGB8, attrib_.viewport.x, attrib_.viewport.y, GL_TRUE);
         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
+        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
+        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
         glBindTexture(GL_TEXTURE_2D_MULTISAMPLE, 0);
 
         // attach the multisampled texture to FBO (framebufferid_  currently binded)
diff --git a/ImageProcessingShader.cpp b/ImageProcessingShader.cpp
index af9b3c8..56b3f62 100644
--- a/ImageProcessingShader.cpp
+++ b/ImageProcessingShader.cpp
@@ -9,13 +9,13 @@ const char* ImageProcessingShader::filter_names[12] = { "None", "Blur", "Sharpen
                                                         "Erosion 3x3", "Erosion 5x5", "Erosion 7x7", "Dilation 3x3", "Dilation 5x5", "Dilation 7x7" };
 
 
-ImageProcessingShader::ImageProcessingShader()
+ImageProcessingShader::ImageProcessingShader(): Shader()
 {
     program_ = &imageProcessingShadingProgram;
     reset();
 }
 
-ImageProcessingShader::ImageProcessingShader(const ImageProcessingShader &S)
+ImageProcessingShader::ImageProcessingShader(const ImageProcessingShader &S): Shader()
 {
     program_ = &imageProcessingShadingProgram;
     reset();
@@ -38,8 +38,6 @@ void ImageProcessingShader::use()
 {
     Shader::use();
 
-//    program_->setUniform("iChannelResolution[0]", iChannelResolution[0].x, iChannelResolution[0].y, iChannelResolution[0].z);
-
     program_->setUniform("brightness", brightness);
     program_->setUniform("contrast", contrast);
     program_->setUniform("saturation", saturation);
@@ -63,9 +61,6 @@ void ImageProcessingShader::reset()
 {
     Shader::reset();
 
-//    // no texture resolution yet
-//    iChannelResolution[0] = glm::vec3(1.f);
-
     // default values for image processing
     brightness = 0.f;
     contrast = 0.f;
diff --git a/ImageProcessingShader.h b/ImageProcessingShader.h
index 23d77fc..d52e48c 100644
--- a/ImageProcessingShader.h
+++ b/ImageProcessingShader.h
@@ -3,7 +3,7 @@
 
 #include <glm/glm.hpp>
 
-#include "Shader.h"
+#include "ImageShader.h"
 
 
 class ImageProcessingShader : public Shader
@@ -19,9 +19,6 @@ public:
 
     void operator = (const ImageProcessingShader &S);
 
-//    // textures resolution
-//    glm::vec3 iChannelResolution[1];
-
     // color effects
     float brightness; // [-1 1]
     float contrast;   // [-1 1]
diff --git a/ImageShader.cpp b/ImageShader.cpp
index 45b32c4..5f96b9d 100644
--- a/ImageShader.cpp
+++ b/ImageShader.cpp
@@ -10,7 +10,7 @@ static ShadingProgram imageShadingProgram("shaders/image.vs", "shaders/image.fs"
 const char* ImageShader::mask_names[11] = { "None", "Glow", "Halo", "Circle", "Round", "Vignette", "Top", "Botton", "Left", "Right", "Custom" };
 std::vector< uint > ImageShader::mask_presets;
 
-ImageShader::ImageShader(): Shader(), mask(0), custom_textureindex(0), stipple(0.0), uv(0.0, 0.0, 1.0, 1.0)
+ImageShader::ImageShader(): Shader(), mask(0), custom_textureindex(0), stipple(0.0)
 {
     // first initialization
     if ( mask_presets.empty() ) {
@@ -36,20 +36,16 @@ void ImageShader::use()
     Shader::use();
 
     program_->setUniform("stipple", stipple);
-    program_->setUniform("uv", uv);
 
     glActiveTexture(GL_TEXTURE1);
-    if ( mask < 10 ) {
+    if ( mask < 10 )
         glBindTexture(GL_TEXTURE_2D, mask_presets[mask]);
-        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
-        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
-    }
     else
         glBindTexture(GL_TEXTURE_2D, custom_textureindex);
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
 
     glActiveTexture(GL_TEXTURE0);
-    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S,  GL_MIRRORED_REPEAT);
-    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T,  GL_MIRRORED_REPEAT);
 
 }
 
@@ -62,9 +58,6 @@ void ImageShader::reset()
     custom_textureindex = mask_presets[0];
     // no stippling
     stipple = 0.f;
-    // normal uv
-    uv = glm::vec4(0.0, 0.0, 1.0, 1.0);
-//    uv = glm::vec4(0.0, 0.0, 2.0, 2.0);
 }
 
 void ImageShader::operator = (const ImageShader &S )
@@ -74,7 +67,6 @@ void ImageShader::operator = (const ImageShader &S )
     mask = S.mask;
     custom_textureindex = S.custom_textureindex;
     stipple = S.stipple;
-    uv = S.uv;
 }
 
 
diff --git a/ImageShader.h b/ImageShader.h
index 9c4ba14..6ad0c0b 100644
--- a/ImageShader.h
+++ b/ImageShader.h
@@ -26,7 +26,6 @@ public:
     uint mask;
     uint custom_textureindex;
     float stipple;
-    glm::vec4 uv;
 
     static const char* mask_names[11];
     static std::vector< uint > mask_presets;
diff --git a/MediaPlayer.cpp b/MediaPlayer.cpp
index 0de9805..f75ebb0 100644
--- a/MediaPlayer.cpp
+++ b/MediaPlayer.cpp
@@ -617,6 +617,8 @@ void MediaPlayer::init_texture(guint index)
                     GL_RGBA, GL_UNSIGNED_BYTE, frame_[index].vframe.data[0]);
     glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
     glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
 
     if (!media_.isimage) {
 
diff --git a/Primitives.cpp b/Primitives.cpp
index 4510d15..d9da99f 100644
--- a/Primitives.cpp
+++ b/Primitives.cpp
@@ -85,8 +85,16 @@ void Surface::draw(glm::mat4 modelview, glm::mat4 projection)
     if ( !initialized() )
         init();
 
-    if ( textureindex_ )
+    glActiveTexture(GL_TEXTURE0);
+    if ( textureindex_ ) {
         glBindTexture(GL_TEXTURE_2D, textureindex_);
+        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S,  GL_MIRRORED_REPEAT);
+        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T,  GL_MIRRORED_REPEAT);
+//        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE); // TODO add user input to select mode
+//        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
+//        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S,  GL_REPEAT);
+//        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T,  GL_REPEAT);
+    }
     else
         glBindTexture(GL_TEXTURE_2D, Resource::getTextureBlack());
 
@@ -97,15 +105,14 @@ void Surface::draw(glm::mat4 modelview, glm::mat4 projection)
 
 void Surface::setTextureUV(glm::vec4 uv)
 {
-    dynamic_cast<ImageShader*>(shader_)->uv = uv;
+    shader_->uv = uv;
 }
 
 glm::vec4 Surface::textureUV() const
 {
-    return dynamic_cast<ImageShader*>(shader_)->uv;
+    return shader_->uv;
 }
 
-
 ImageSurface::ImageSurface(const std::string& path, Shader *s) : Surface(s), resource_(path)
 {
 
diff --git a/Resource.cpp b/Resource.cpp
index 98645e3..bd0bda9 100644
--- a/Resource.cpp
+++ b/Resource.cpp
@@ -33,6 +33,10 @@ uint Resource::getTextureBlack()
     if (tex_index_black == 0) {
         glGenTextures(1, &tex_index_black);
         glBindTexture( GL_TEXTURE_2D, tex_index_black);
+        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
+        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
+        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
+        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
         unsigned char clearColor[4] = {0, 0, 0, 255};
         // texture with one black pixel
         glTexStorage2D(GL_TEXTURE_2D, 1, GL_RGBA8, 1, 1);
@@ -50,6 +54,10 @@ uint Resource::getTextureWhite()
     if (tex_index_white == 0) {
         glGenTextures(1, &tex_index_white);
         glBindTexture( GL_TEXTURE_2D, tex_index_white);
+        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
+        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
+        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
+        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
         unsigned char clearColor[4] = {255, 255, 255, 255};
         // texture with one black pixel
         glTexStorage2D(GL_TEXTURE_2D, 1, GL_RGBA8, 1, 1);
@@ -67,6 +75,10 @@ uint Resource::getTextureTransparent()
     if (tex_index_transparent == 0) {
         glGenTextures(1, &tex_index_transparent);
         glBindTexture( GL_TEXTURE_2D, tex_index_transparent);
+        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
+        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
+        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
+        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
         unsigned char clearColor[4] = {0, 0, 0, 0};
         // texture with one black pixel
         glTexStorage2D(GL_TEXTURE_2D, 1, GL_RGBA8, 1, 1);
@@ -265,6 +277,8 @@ uint Resource::getTextureImage(const std::string& path, float *aspect_ratio)
     glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, w, h, GL_RGBA, GL_UNSIGNED_BYTE, img);
     glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
     glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
 
     // free memory
 	stbi_image_free(img);
diff --git a/SessionCreator.cpp b/SessionCreator.cpp
index e210007..3eb86bd 100644
--- a/SessionCreator.cpp
+++ b/SessionCreator.cpp
@@ -431,9 +431,9 @@ void SessionLoader::visit(ImageShader &n)
         uniforms->QueryUnsignedAttribute("mask", &n.mask);
     }
 
-    XMLElement* uvtex = xmlCurrent_->FirstChildElement("uv");
-    if (uvtex)
-        tinyxml2::XMLElementToGLM( uvtex->FirstChildElement("vec4"), n.uv);
+//    XMLElement* uvtex = xmlCurrent_->FirstChildElement("uv");
+//    if (uvtex)
+//        tinyxml2::XMLElementToGLM( uvtex->FirstChildElement("vec4"), n.uv);
 }
 
 void SessionLoader::visit(ImageProcessingShader &n)
diff --git a/SessionVisitor.cpp b/SessionVisitor.cpp
index e4fe65d..a6bedd4 100644
--- a/SessionVisitor.cpp
+++ b/SessionVisitor.cpp
@@ -202,9 +202,9 @@ void SessionVisitor::visit(ImageShader &n)
     uniforms->SetAttribute("mask", n.mask);
     xmlCurrent_->InsertEndChild(uniforms);
 
-    XMLElement *uvtex = xmlDoc_->NewElement("uv");
-    uvtex->InsertEndChild( XMLElementFromGLM(xmlDoc_, n.uv) );
-    xmlCurrent_->InsertEndChild(uvtex);
+//    XMLElement *uvtex = xmlDoc_->NewElement("uv");
+//    uvtex->InsertEndChild( XMLElementFromGLM(xmlDoc_, n.uv) );
+//    xmlCurrent_->InsertEndChild(uvtex);
 
 }
 
diff --git a/Shader.cpp b/Shader.cpp
index cfe9f71..b0fb0ad 100644
--- a/Shader.cpp
+++ b/Shader.cpp
@@ -186,6 +186,7 @@ void Shader::operator = (const Shader &S )
 {
     color = S.color;
     blending = S.blending;
+    uv = S.uv;
 }
 
 void Shader::accept(Visitor& v) {
@@ -205,6 +206,7 @@ void Shader::use()
     program_->setUniform("projection", projection);
     program_->setUniform("modelview", modelview);
     program_->setUniform("color", color);
+    program_->setUniform("uv", uv);
 
     iResolution = glm::vec3( Rendering::manager().currentAttrib().viewport, 0.f);
     program_->setUniform("iResolution", iResolution);
@@ -237,6 +239,7 @@ void Shader::reset()
     modelview  = glm::identity<glm::mat4>();
     iResolution = glm::vec3(1280.f, 720.f, 0.f);
     color = glm::vec4(1.f, 1.f, 1.f, 1.f);
+    uv = glm::vec4(0.0, 0.0, 1.0, 1.0);
 }
 
 
diff --git a/Shader.h b/Shader.h
index 834fc05..fedd548 100644
--- a/Shader.h
+++ b/Shader.h
@@ -55,6 +55,7 @@ public:
     glm::mat4 projection;
     glm::mat4 modelview;
     glm::vec4 color;
+    glm::vec4 uv;
 
     typedef enum {
         BLEND_OPACITY = 0,
diff --git a/Source.cpp b/Source.cpp
index dfded20..102a539 100644
--- a/Source.cpp
+++ b/Source.cpp
@@ -434,18 +434,19 @@ void Source::update(float dt)
         groups_[View::RENDERING]->translation_.z = groups_[View::LAYER]->translation_.z;
 
         // MODIFY texture projection based on APPEARANCE node
-        texturesurface_->translation_.x = groups_[View::APPEARANCE]->translation_.x;
+        glm::vec3 center = groups_[View::APPEARANCE]->translation_;
         if (renderbuffer_)
-            texturesurface_->translation_.x /= renderbuffer_->aspectRatio();
-        texturesurface_->translation_.y = groups_[View::APPEARANCE]->translation_.y;
-        texturesurface_->rotation_.z = groups_[View::APPEARANCE]->rotation_.z;
-        // avoid any null scale
-        s = groups_[View::APPEARANCE]->scale_;
-        s.x = CLAMP_SCALE(s.x);
-        s.y = CLAMP_SCALE(s.y);
-        s.z = 1.f;
-        texturesurface_->scale_ = s;
-        texturesurface_->update(dt);
+            center.x /= renderbuffer_->aspectRatio();
+        glm::vec3 UL = glm::vec3(-1.f, 1.f, 0.f) - center;
+        glm::vec3 BR = glm::vec3(1.f, -1.f, 0.f) - center;
+        UL /= groups_[View::APPEARANCE]->scale_;
+        BR /= groups_[View::APPEARANCE]->scale_;
+        glm::vec4 uv;
+        uv.x = UL.x * 0.5f + 0.5f;
+        uv.y = UL.y * -0.5f + 0.5f;
+        uv.z = BR.x * 0.5f + 0.5f;
+        uv.w = BR.y * -0.5f + 0.5f;
+        texturesurface_->setTextureUV(uv);
 
         need_update_ = false;
     }
diff --git a/Stream.cpp b/Stream.cpp
index 955c90a..fc80743 100644
--- a/Stream.cpp
+++ b/Stream.cpp
@@ -365,7 +365,8 @@ void Stream::init_texture(guint index)
                     GL_RGBA, GL_UNSIGNED_BYTE, frame_[index].vframe.data[0]);
     glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
     glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
-
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
 
     // set pbo image size
     pbo_size_ = height_ * width_ * 4;
diff --git a/View.cpp b/View.cpp
index 01795a6..14e7ed8 100644
--- a/View.cpp
+++ b/View.cpp
@@ -604,6 +604,8 @@ uint MixingView::textureMixingQuadratic()
         glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, CIRCLE_PIXELS, CIRCLE_PIXELS, GL_BGRA, GL_UNSIGNED_BYTE, matrix);
         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
+        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
+        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
 
     }
     return texid;
@@ -1836,41 +1838,6 @@ void AppearanceView::draw()
 
 View::Cursor AppearanceView::grab (Source *s, glm::vec2 from, glm::vec2 to, std::pair<Node *, glm::vec2> pick)
 {
-//    View::Cursor ret = Cursor();
-//    std::ostringstream info;
-
-//    // work on the given source
-//    if (!s)
-//        return ret;
-
-//    Group *sourceNode = s->group(mode_); // groups_[View::APPEARANCE]
-
-//    // grab coordinates in scene-View reference frame
-//    glm::vec3 scene_from = Rendering::manager().unProject(from, scene.root()->transform_);
-//    glm::vec3 scene_to   = Rendering::manager().unProject(to, scene.root()->transform_);
-//    glm::vec3 scene_translation = scene_to - scene_from;
-
-//    // make sure matrix transform of stored status is updated
-//    s->stored_status_->update(0);
-
-//    ret.type = Cursor_ResizeAll;
-//    info << "UV " ;
-
-//    sourceNode->translation_ = s->stored_status_->translation_ + scene_translation;
-
-////    ImageShader *shader = s->blendingShader ();
-////    shader->uv.x += scene_translation.x;
-////    shader->uv.y += scene_translation.y;
-////    shader->uv.z += scene_translation.x;
-////    shader->uv.w += scene_translation.y;
-
-
-//    // request update
-//    s->touch();
-
-//    // update cursor
-//    ret.info = info.str();
-//    return ret;
     View::Cursor ret = Cursor();
 
     // work on the given source
diff --git a/rsc/shaders/image.fs b/rsc/shaders/image.fs
index 4d123bd..61a1ffc 100644
--- a/rsc/shaders/image.fs
+++ b/rsc/shaders/image.fs
@@ -5,13 +5,15 @@ out vec4 FragColor;
 in vec4 vertexColor;
 in vec2 vertexUV;
 
+// from General Shader
+uniform vec3 iResolution;           // viewport resolution (in pixels)
+uniform vec4 color;
+uniform vec4 uv;
+
+// Image Shader
 uniform sampler2D iChannel0;             // input channel (texture id).
 uniform sampler2D iChannel1;             // input mask
-uniform vec3      iResolution;           // viewport resolution (in pixels)
-
-uniform vec4 color;
 uniform float stipple;
-uniform vec4 uv;
 
 void main()
 {
diff --git a/rsc/shaders/imageblending.fs b/rsc/shaders/imageblending.fs
new file mode 100644
index 0000000..61a1ffc
--- /dev/null
+++ b/rsc/shaders/imageblending.fs
@@ -0,0 +1,36 @@
+#version 330 core
+
+out vec4 FragColor;
+
+in vec4 vertexColor;
+in vec2 vertexUV;
+
+// from General Shader
+uniform vec3 iResolution;           // viewport resolution (in pixels)
+uniform vec4 color;
+uniform vec4 uv;
+
+// Image Shader
+uniform sampler2D iChannel0;             // input channel (texture id).
+uniform sampler2D iChannel1;             // input mask
+uniform float stipple;
+
+void main()
+{
+    // adjust UV
+    vec2 texcoord = vec2(uv.x, uv.y) + vertexUV * vec2(uv.z - uv.x, uv.w - uv.y);
+
+    // color is a mix of texture (manipulated with brightness & contrast), vertex and uniform colors
+    vec4 textureColor = texture(iChannel0, texcoord);
+    vec3 RGB = textureColor.rgb * vertexColor.rgb * color.rgb;
+
+    // alpha is a mix of texture alpha, vertex alpha, and uniform alpha affected by stippling
+    vec4 maskColor = texture(iChannel1, vertexUV);
+    float maskIntensity = (maskColor.r + maskColor.g + maskColor.b) / 3.0;
+
+    float A = textureColor.a * vertexColor.a * color.a * maskIntensity;
+    A -= stipple * ( int(gl_FragCoord.x + gl_FragCoord.y) % 2 > 0 ? 0.05 : 0.95 );
+
+    // output RGBA
+    FragColor = vec4(RGB, clamp(A, 0.0, 1.0) );
+}
diff --git a/rsc/shaders/imageprocessing.fs b/rsc/shaders/imageprocessing.fs
index 15e22d3..7e3a029 100644
--- a/rsc/shaders/imageprocessing.fs
+++ b/rsc/shaders/imageprocessing.fs
@@ -25,14 +25,17 @@ out vec4 FragColor;
 in vec4 vertexColor;
 in vec2 vertexUV;
 
-// general shader uniforms
-uniform vec4 color;
+vec2 texcoord;
 
 // image processing specific
-uniform sampler2D iChannel0;  // input channel (texture id).
-//uniform vec3      iChannelResolution[1]; // replaced by textureSize(iChannel0, 0);
+uniform sampler2D iChannel0;             // input channel (texture id).
 uniform vec3      iResolution;           // viewport resolution (in pixels)
 
+// Image shader uniforms
+uniform vec4 color;
+uniform vec4 uv;
+
+// Image processing uniforms
 uniform float contrast;
 uniform float brightness;
 uniform float saturation;
@@ -74,47 +77,47 @@ vec3 erosion(int N, vec2 filter_step)
 {
     vec3 minValue = vec3(1.0);
 
-    minValue = min(texture(iChannel0, vertexUV + vec2 (0.0,0.0) * filter_step ).rgb, minValue);
-    minValue = min(texture(iChannel0, vertexUV + vec2 (0.0,-1.0) * filter_step ).rgb, minValue);
-    minValue = min(texture(iChannel0, vertexUV + vec2 (-1.0, 0.0) * filter_step ).rgb, minValue);
-    minValue = min(texture(iChannel0, vertexUV + vec2 (1.0, 0.0) * filter_step ).rgb, minValue);
-    minValue = min(texture(iChannel0, vertexUV + vec2 (0.0, 1.0) * filter_step ).rgb, minValue);
+    minValue = min(texture(iChannel0, texcoord + vec2 (0.0,0.0) * filter_step ).rgb, minValue);
+    minValue = min(texture(iChannel0, texcoord + vec2 (0.0,-1.0) * filter_step ).rgb, minValue);
+    minValue = min(texture(iChannel0, texcoord + vec2 (-1.0, 0.0) * filter_step ).rgb, minValue);
+    minValue = min(texture(iChannel0, texcoord + vec2 (1.0, 0.0) * filter_step ).rgb, minValue);
+    minValue = min(texture(iChannel0, texcoord + vec2 (0.0, 1.0) * filter_step ).rgb, minValue);
     if (N < 1)
         return minValue;
-    minValue = min(texture(iChannel0, vertexUV + vec2 (-1.0, -2.0) * filter_step ).rgb, minValue);
-    minValue = min(texture(iChannel0, vertexUV + vec2 (0.0,-2.0) * filter_step ).rgb, minValue);
-    minValue = min(texture(iChannel0, vertexUV + vec2 (1.0,-2.0) * filter_step ).rgb, minValue);
-    minValue = min(texture(iChannel0, vertexUV + vec2 (-1.0,2.0) * filter_step ).rgb, minValue);
-    minValue = min(texture(iChannel0, vertexUV + vec2 (0.0, 2.0) * filter_step ).rgb, minValue);
-    minValue = min(texture(iChannel0, vertexUV + vec2 (1.0, 2.0) * filter_step ).rgb, minValue);
-    minValue = min(texture(iChannel0, vertexUV + vec2 (-2.0, 1.0) * filter_step ).rgb, minValue);
-    minValue = min(texture(iChannel0, vertexUV + vec2 (-1.0, 1.0) * filter_step ).rgb, minValue);
-    minValue = min(texture(iChannel0, vertexUV + vec2 ( 1.0, 1.0) * filter_step ).rgb, minValue);
-    minValue = min(texture(iChannel0, vertexUV + vec2 ( 2.0, 1.0) * filter_step ).rgb, minValue);
-    minValue = min(texture(iChannel0, vertexUV + vec2 (-2.0, -1.0) * filter_step ).rgb, minValue);
-    minValue = min(texture(iChannel0, vertexUV + vec2 (-1.0, -1.0) * filter_step ).rgb, minValue);
-    minValue = min(texture(iChannel0, vertexUV + vec2 ( 1.0, -1.0) * filter_step ).rgb, minValue);
-    minValue = min(texture(iChannel0, vertexUV + vec2 ( 2.0, -1.0) * filter_step ).rgb, minValue);
-    minValue = min(texture(iChannel0, vertexUV + vec2 (-2.0, 0.0) * filter_step ).rgb, minValue);
-    minValue = min(texture(iChannel0, vertexUV + vec2 ( 2.0, 0.0) * filter_step ).rgb, minValue);
+    minValue = min(texture(iChannel0, texcoord + vec2 (-1.0, -2.0) * filter_step ).rgb, minValue);
+    minValue = min(texture(iChannel0, texcoord + vec2 (0.0,-2.0) * filter_step ).rgb, minValue);
+    minValue = min(texture(iChannel0, texcoord + vec2 (1.0,-2.0) * filter_step ).rgb, minValue);
+    minValue = min(texture(iChannel0, texcoord + vec2 (-1.0,2.0) * filter_step ).rgb, minValue);
+    minValue = min(texture(iChannel0, texcoord + vec2 (0.0, 2.0) * filter_step ).rgb, minValue);
+    minValue = min(texture(iChannel0, texcoord + vec2 (1.0, 2.0) * filter_step ).rgb, minValue);
+    minValue = min(texture(iChannel0, texcoord + vec2 (-2.0, 1.0) * filter_step ).rgb, minValue);
+    minValue = min(texture(iChannel0, texcoord + vec2 (-1.0, 1.0) * filter_step ).rgb, minValue);
+    minValue = min(texture(iChannel0, texcoord + vec2 ( 1.0, 1.0) * filter_step ).rgb, minValue);
+    minValue = min(texture(iChannel0, texcoord + vec2 ( 2.0, 1.0) * filter_step ).rgb, minValue);
+    minValue = min(texture(iChannel0, texcoord + vec2 (-2.0, -1.0) * filter_step ).rgb, minValue);
+    minValue = min(texture(iChannel0, texcoord + vec2 (-1.0, -1.0) * filter_step ).rgb, minValue);
+    minValue = min(texture(iChannel0, texcoord + vec2 ( 1.0, -1.0) * filter_step ).rgb, minValue);
+    minValue = min(texture(iChannel0, texcoord + vec2 ( 2.0, -1.0) * filter_step ).rgb, minValue);
+    minValue = min(texture(iChannel0, texcoord + vec2 (-2.0, 0.0) * filter_step ).rgb, minValue);
+    minValue = min(texture(iChannel0, texcoord + vec2 ( 2.0, 0.0) * filter_step ).rgb, minValue);
     if (N < 2)
         return minValue;
-    minValue = min(texture(iChannel0, vertexUV + vec2 (-1.0, -3.0) * filter_step ).rgb, minValue);
-    minValue = min(texture(iChannel0, vertexUV + vec2 (0.0,-3.0) * filter_step ).rgb, minValue);
-    minValue = min(texture(iChannel0, vertexUV + vec2 (1.0,-3.0) * filter_step ).rgb, minValue);
-    minValue = min(texture(iChannel0, vertexUV + vec2 (-1.0,3.0) * filter_step ).rgb, minValue);
-    minValue = min(texture(iChannel0, vertexUV + vec2 (0.0, 3.0) * filter_step ).rgb, minValue);
-    minValue = min(texture(iChannel0, vertexUV + vec2 (1.0, 3.0) * filter_step ).rgb, minValue);
-    minValue = min(texture(iChannel0, vertexUV + vec2 (-2.0, 2.0) * filter_step ).rgb, minValue);
-    minValue = min(texture(iChannel0, vertexUV + vec2 ( 2.0, 2.0) * filter_step ).rgb, minValue);
-    minValue = min(texture(iChannel0, vertexUV + vec2 (-2.0, -2.0) * filter_step ).rgb, minValue);
-    minValue = min(texture(iChannel0, vertexUV + vec2 ( 2.0, -2.0) * filter_step ).rgb, minValue);
-    minValue = min(texture(iChannel0, vertexUV + vec2 (-3.0, -1.0) * filter_step ).rgb, minValue);
-    minValue = min(texture(iChannel0, vertexUV + vec2 (3.0, -1.0) * filter_step ).rgb, minValue);
-    minValue = min(texture(iChannel0, vertexUV + vec2 (-3.0, 1.0) * filter_step ).rgb, minValue);
-    minValue = min(texture(iChannel0, vertexUV + vec2 ( 3.0, 1.0) * filter_step ).rgb, minValue);
-    minValue = min(texture(iChannel0, vertexUV + vec2 (-3.0, 0.0) * filter_step ).rgb, minValue);
-    minValue = min(texture(iChannel0, vertexUV + vec2 ( 3.0, 0.0) * filter_step ).rgb, minValue);
+    minValue = min(texture(iChannel0, texcoord + vec2 (-1.0, -3.0) * filter_step ).rgb, minValue);
+    minValue = min(texture(iChannel0, texcoord + vec2 (0.0,-3.0) * filter_step ).rgb, minValue);
+    minValue = min(texture(iChannel0, texcoord + vec2 (1.0,-3.0) * filter_step ).rgb, minValue);
+    minValue = min(texture(iChannel0, texcoord + vec2 (-1.0,3.0) * filter_step ).rgb, minValue);
+    minValue = min(texture(iChannel0, texcoord + vec2 (0.0, 3.0) * filter_step ).rgb, minValue);
+    minValue = min(texture(iChannel0, texcoord + vec2 (1.0, 3.0) * filter_step ).rgb, minValue);
+    minValue = min(texture(iChannel0, texcoord + vec2 (-2.0, 2.0) * filter_step ).rgb, minValue);
+    minValue = min(texture(iChannel0, texcoord + vec2 ( 2.0, 2.0) * filter_step ).rgb, minValue);
+    minValue = min(texture(iChannel0, texcoord + vec2 (-2.0, -2.0) * filter_step ).rgb, minValue);
+    minValue = min(texture(iChannel0, texcoord + vec2 ( 2.0, -2.0) * filter_step ).rgb, minValue);
+    minValue = min(texture(iChannel0, texcoord + vec2 (-3.0, -1.0) * filter_step ).rgb, minValue);
+    minValue = min(texture(iChannel0, texcoord + vec2 (3.0, -1.0) * filter_step ).rgb, minValue);
+    minValue = min(texture(iChannel0, texcoord + vec2 (-3.0, 1.0) * filter_step ).rgb, minValue);
+    minValue = min(texture(iChannel0, texcoord + vec2 ( 3.0, 1.0) * filter_step ).rgb, minValue);
+    minValue = min(texture(iChannel0, texcoord + vec2 (-3.0, 0.0) * filter_step ).rgb, minValue);
+    minValue = min(texture(iChannel0, texcoord + vec2 ( 3.0, 0.0) * filter_step ).rgb, minValue);
 
     return minValue;
 }
@@ -123,47 +126,47 @@ vec3 dilation(int N, vec2 filter_step)
 {
     vec3 maxValue = vec3(0.0);
 
-    maxValue = max(texture(iChannel0, vertexUV + vec2 (0.0, 0.0) * filter_step ).rgb, maxValue);
-    maxValue = max(texture(iChannel0, vertexUV + vec2 (0.0,-1.0) * filter_step ).rgb, maxValue);
-    maxValue = max(texture(iChannel0, vertexUV + vec2 (-1.0, 0.0) * filter_step ).rgb, maxValue);
-    maxValue = max(texture(iChannel0, vertexUV + vec2 (1.0, 0.0) * filter_step ).rgb, maxValue);
-    maxValue = max(texture(iChannel0, vertexUV + vec2 (0.0, 1.0) * filter_step ).rgb, maxValue);
+    maxValue = max(texture(iChannel0, texcoord + vec2 (0.0, 0.0) * filter_step ).rgb, maxValue);
+    maxValue = max(texture(iChannel0, texcoord + vec2 (0.0,-1.0) * filter_step ).rgb, maxValue);
+    maxValue = max(texture(iChannel0, texcoord + vec2 (-1.0, 0.0) * filter_step ).rgb, maxValue);
+    maxValue = max(texture(iChannel0, texcoord + vec2 (1.0, 0.0) * filter_step ).rgb, maxValue);
+    maxValue = max(texture(iChannel0, texcoord + vec2 (0.0, 1.0) * filter_step ).rgb, maxValue);
     if (N < 1)
         return maxValue;
-    maxValue = max(texture(iChannel0, vertexUV + vec2 (-1.0, -2.0) * filter_step ).rgb, maxValue);
-    maxValue = max(texture(iChannel0, vertexUV + vec2 (0.0,-2.0) * filter_step ).rgb, maxValue);
-    maxValue = max(texture(iChannel0, vertexUV + vec2 (1.0,-2.0) * filter_step ).rgb, maxValue);
-    maxValue = max(texture(iChannel0, vertexUV + vec2 (-1.0,2.0) * filter_step ).rgb, maxValue);
-    maxValue = max(texture(iChannel0, vertexUV + vec2 (0.0, 2.0) * filter_step ).rgb, maxValue);
-    maxValue = max(texture(iChannel0, vertexUV + vec2 (1.0, 2.0) * filter_step ).rgb, maxValue);
-    maxValue = max(texture(iChannel0, vertexUV + vec2 (-2.0, 1.0) * filter_step ).rgb, maxValue);
-    maxValue = max(texture(iChannel0, vertexUV + vec2 (-1.0, 1.0) * filter_step ).rgb, maxValue);
-    maxValue = max(texture(iChannel0, vertexUV + vec2 ( 1.0, 1.0) * filter_step ).rgb, maxValue);
-    maxValue = max(texture(iChannel0, vertexUV + vec2 ( 2.0, 1.0) * filter_step ).rgb, maxValue);
-    maxValue = max(texture(iChannel0, vertexUV + vec2 (-2.0, -1.0) * filter_step ).rgb, maxValue);
-    maxValue = max(texture(iChannel0, vertexUV + vec2 (-1.0, -1.0) * filter_step ).rgb, maxValue);
-    maxValue = max(texture(iChannel0, vertexUV + vec2 ( 1.0, -1.0) * filter_step ).rgb, maxValue);
-    maxValue = max(texture(iChannel0, vertexUV + vec2 ( 2.0, -1.0) * filter_step ).rgb, maxValue);
-    maxValue = max(texture(iChannel0, vertexUV + vec2 (-2.0, 0.0) * filter_step ).rgb, maxValue);
-    maxValue = max(texture(iChannel0, vertexUV + vec2 ( 2.0, 0.0) * filter_step ).rgb, maxValue);
+    maxValue = max(texture(iChannel0, texcoord + vec2 (-1.0, -2.0) * filter_step ).rgb, maxValue);
+    maxValue = max(texture(iChannel0, texcoord + vec2 (0.0,-2.0) * filter_step ).rgb, maxValue);
+    maxValue = max(texture(iChannel0, texcoord + vec2 (1.0,-2.0) * filter_step ).rgb, maxValue);
+    maxValue = max(texture(iChannel0, texcoord + vec2 (-1.0,2.0) * filter_step ).rgb, maxValue);
+    maxValue = max(texture(iChannel0, texcoord + vec2 (0.0, 2.0) * filter_step ).rgb, maxValue);
+    maxValue = max(texture(iChannel0, texcoord + vec2 (1.0, 2.0) * filter_step ).rgb, maxValue);
+    maxValue = max(texture(iChannel0, texcoord + vec2 (-2.0, 1.0) * filter_step ).rgb, maxValue);
+    maxValue = max(texture(iChannel0, texcoord + vec2 (-1.0, 1.0) * filter_step ).rgb, maxValue);
+    maxValue = max(texture(iChannel0, texcoord + vec2 ( 1.0, 1.0) * filter_step ).rgb, maxValue);
+    maxValue = max(texture(iChannel0, texcoord + vec2 ( 2.0, 1.0) * filter_step ).rgb, maxValue);
+    maxValue = max(texture(iChannel0, texcoord + vec2 (-2.0, -1.0) * filter_step ).rgb, maxValue);
+    maxValue = max(texture(iChannel0, texcoord + vec2 (-1.0, -1.0) * filter_step ).rgb, maxValue);
+    maxValue = max(texture(iChannel0, texcoord + vec2 ( 1.0, -1.0) * filter_step ).rgb, maxValue);
+    maxValue = max(texture(iChannel0, texcoord + vec2 ( 2.0, -1.0) * filter_step ).rgb, maxValue);
+    maxValue = max(texture(iChannel0, texcoord + vec2 (-2.0, 0.0) * filter_step ).rgb, maxValue);
+    maxValue = max(texture(iChannel0, texcoord + vec2 ( 2.0, 0.0) * filter_step ).rgb, maxValue);
     if (N < 2)
         return maxValue;
-    maxValue = max(texture(iChannel0, vertexUV + vec2 (-1.0, -3.0) * filter_step ).rgb, maxValue);
-    maxValue = max(texture(iChannel0, vertexUV + vec2 (0.0,-3.0) * filter_step ).rgb, maxValue);
-    maxValue = max(texture(iChannel0, vertexUV + vec2 (1.0,-3.0) * filter_step ).rgb, maxValue);
-    maxValue = max(texture(iChannel0, vertexUV + vec2 (-1.0,3.0) * filter_step ).rgb, maxValue);
-    maxValue = max(texture(iChannel0, vertexUV + vec2 (0.0, 3.0) * filter_step ).rgb, maxValue);
-    maxValue = max(texture(iChannel0, vertexUV + vec2 (1.0, 3.0) * filter_step ).rgb, maxValue);
-    maxValue = max(texture(iChannel0, vertexUV + vec2 (-2.0, 2.0) * filter_step ).rgb, maxValue);
-    maxValue = max(texture(iChannel0, vertexUV + vec2 ( 2.0, 2.0) * filter_step ).rgb, maxValue);
-    maxValue = max(texture(iChannel0, vertexUV + vec2 (-2.0, -2.0) * filter_step ).rgb, maxValue);
-    maxValue = max(texture(iChannel0, vertexUV + vec2 ( 2.0, -2.0) * filter_step ).rgb, maxValue);
-    maxValue = max(texture(iChannel0, vertexUV + vec2 (-3.0, -1.0) * filter_step ).rgb, maxValue);
-    maxValue = max(texture(iChannel0, vertexUV + vec2 (3.0, -1.0) * filter_step ).rgb, maxValue);
-    maxValue = max(texture(iChannel0, vertexUV + vec2 (-3.0, 1.0) * filter_step ).rgb, maxValue);
-    maxValue = max(texture(iChannel0, vertexUV + vec2 ( 3.0, 1.0) * filter_step ).rgb, maxValue);
-    maxValue = max(texture(iChannel0, vertexUV + vec2 (-3.0, 0.0) * filter_step ).rgb, maxValue);
-    maxValue = max(texture(iChannel0, vertexUV + vec2 ( 3.0, 0.0) * filter_step ).rgb, maxValue);
+    maxValue = max(texture(iChannel0, texcoord + vec2 (-1.0, -3.0) * filter_step ).rgb, maxValue);
+    maxValue = max(texture(iChannel0, texcoord + vec2 (0.0,-3.0) * filter_step ).rgb, maxValue);
+    maxValue = max(texture(iChannel0, texcoord + vec2 (1.0,-3.0) * filter_step ).rgb, maxValue);
+    maxValue = max(texture(iChannel0, texcoord + vec2 (-1.0,3.0) * filter_step ).rgb, maxValue);
+    maxValue = max(texture(iChannel0, texcoord + vec2 (0.0, 3.0) * filter_step ).rgb, maxValue);
+    maxValue = max(texture(iChannel0, texcoord + vec2 (1.0, 3.0) * filter_step ).rgb, maxValue);
+    maxValue = max(texture(iChannel0, texcoord + vec2 (-2.0, 2.0) * filter_step ).rgb, maxValue);
+    maxValue = max(texture(iChannel0, texcoord + vec2 ( 2.0, 2.0) * filter_step ).rgb, maxValue);
+    maxValue = max(texture(iChannel0, texcoord + vec2 (-2.0, -2.0) * filter_step ).rgb, maxValue);
+    maxValue = max(texture(iChannel0, texcoord + vec2 ( 2.0, -2.0) * filter_step ).rgb, maxValue);
+    maxValue = max(texture(iChannel0, texcoord + vec2 (-3.0, -1.0) * filter_step ).rgb, maxValue);
+    maxValue = max(texture(iChannel0, texcoord + vec2 (3.0, -1.0) * filter_step ).rgb, maxValue);
+    maxValue = max(texture(iChannel0, texcoord + vec2 (-3.0, 1.0) * filter_step ).rgb, maxValue);
+    maxValue = max(texture(iChannel0, texcoord + vec2 ( 3.0, 1.0) * filter_step ).rgb, maxValue);
+    maxValue = max(texture(iChannel0, texcoord + vec2 (-3.0, 0.0) * filter_step ).rgb, maxValue);
+    maxValue = max(texture(iChannel0, texcoord + vec2 ( 3.0, 0.0) * filter_step ).rgb, maxValue);
 
     return maxValue;
 }
@@ -173,29 +176,29 @@ vec3 opening(vec2 filter_step)
 {
     // 1) erosion
     vec3 minValue1 = vec3(1.0);
-    minValue1 = min(texture(iChannel0, vertexUV + vec2 (0.0, 0.0) * filter_step ).rgb, minValue1);
-    minValue1 = min(texture(iChannel0, vertexUV + vec2 (0.0, 1.0) * filter_step ).rgb, minValue1);
-    minValue1 = min(texture(iChannel0, vertexUV + vec2 (0.0, 2.0) * filter_step ).rgb, minValue1);
-    minValue1 = min(texture(iChannel0, vertexUV + vec2 (1.0, 1.0) * filter_step ).rgb, minValue1);
-    minValue1 = min(texture(iChannel0, vertexUV + vec2 (1.0, -1.0) * filter_step ).rgb, minValue1);
+    minValue1 = min(texture(iChannel0, texcoord + vec2 (0.0, 0.0) * filter_step ).rgb, minValue1);
+    minValue1 = min(texture(iChannel0, texcoord + vec2 (0.0, 1.0) * filter_step ).rgb, minValue1);
+    minValue1 = min(texture(iChannel0, texcoord + vec2 (0.0, 2.0) * filter_step ).rgb, minValue1);
+    minValue1 = min(texture(iChannel0, texcoord + vec2 (1.0, 1.0) * filter_step ).rgb, minValue1);
+    minValue1 = min(texture(iChannel0, texcoord + vec2 (1.0, -1.0) * filter_step ).rgb, minValue1);
     vec3 minValue2 = vec3(1.0);
-    minValue2 = min(texture(iChannel0, vertexUV + vec2 (0.0, 0.0) * filter_step ).rgb, minValue2);
-    minValue2 = min(texture(iChannel0, vertexUV + vec2 (-1.0, 0.0) * filter_step ).rgb, minValue2);
-    minValue2 = min(texture(iChannel0, vertexUV + vec2 (-2.0, 0.0) * filter_step ).rgb, minValue2);
-    minValue2 = min(texture(iChannel0, vertexUV + vec2 (1.0, -1.0) * filter_step ).rgb, minValue2);
-    minValue2 = min(texture(iChannel0, vertexUV + vec2 (-1.0, -1.0) * filter_step ).rgb, minValue2);
+    minValue2 = min(texture(iChannel0, texcoord + vec2 (0.0, 0.0) * filter_step ).rgb, minValue2);
+    minValue2 = min(texture(iChannel0, texcoord + vec2 (-1.0, 0.0) * filter_step ).rgb, minValue2);
+    minValue2 = min(texture(iChannel0, texcoord + vec2 (-2.0, 0.0) * filter_step ).rgb, minValue2);
+    minValue2 = min(texture(iChannel0, texcoord + vec2 (1.0, -1.0) * filter_step ).rgb, minValue2);
+    minValue2 = min(texture(iChannel0, texcoord + vec2 (-1.0, -1.0) * filter_step ).rgb, minValue2);
     vec3 minValue3 = vec3(1.0);
-    minValue3 = min(texture(iChannel0, vertexUV + vec2 (0.0, 0.0) * filter_step ).rgb, minValue3);
-    minValue3 = min(texture(iChannel0, vertexUV + vec2 (0.0, -1.0) * filter_step ).rgb, minValue3);
-    minValue3 = min(texture(iChannel0, vertexUV + vec2 (0.0, -2.0) * filter_step ).rgb, minValue3);
-    minValue3 = min(texture(iChannel0, vertexUV + vec2 (-1.0, -1.0) * filter_step ).rgb, minValue3);
-    minValue3 = min(texture(iChannel0, vertexUV + vec2 (-1.0, 1.0) * filter_step ).rgb, minValue3);
+    minValue3 = min(texture(iChannel0, texcoord + vec2 (0.0, 0.0) * filter_step ).rgb, minValue3);
+    minValue3 = min(texture(iChannel0, texcoord + vec2 (0.0, -1.0) * filter_step ).rgb, minValue3);
+    minValue3 = min(texture(iChannel0, texcoord + vec2 (0.0, -2.0) * filter_step ).rgb, minValue3);
+    minValue3 = min(texture(iChannel0, texcoord + vec2 (-1.0, -1.0) * filter_step ).rgb, minValue3);
+    minValue3 = min(texture(iChannel0, texcoord + vec2 (-1.0, 1.0) * filter_step ).rgb, minValue3);
     vec3 minValue4 = vec3(1.0);
-    minValue4 = min(texture(iChannel0, vertexUV + vec2 (0.0, 0.0) * filter_step ).rgb, minValue4);
-    minValue4 = min(texture(iChannel0, vertexUV + vec2 (1.0, 0.0) * filter_step ).rgb, minValue4);
-    minValue4 = min(texture(iChannel0, vertexUV + vec2 (2.0, 0.0) * filter_step ).rgb, minValue4);
-    minValue4 = min(texture(iChannel0, vertexUV + vec2 (1.0, 1.0) * filter_step ).rgb, minValue4);
-    minValue4 = min(texture(iChannel0, vertexUV + vec2 (-1.0, 1.0) * filter_step ).rgb, minValue4);
+    minValue4 = min(texture(iChannel0, texcoord + vec2 (0.0, 0.0) * filter_step ).rgb, minValue4);
+    minValue4 = min(texture(iChannel0, texcoord + vec2 (1.0, 0.0) * filter_step ).rgb, minValue4);
+    minValue4 = min(texture(iChannel0, texcoord + vec2 (2.0, 0.0) * filter_step ).rgb, minValue4);
+    minValue4 = min(texture(iChannel0, texcoord + vec2 (1.0, 1.0) * filter_step ).rgb, minValue4);
+    minValue4 = min(texture(iChannel0, texcoord + vec2 (-1.0, 1.0) * filter_step ).rgb, minValue4);
 
     // 2) dilation
     vec3 maxValue = vec3(0.0);
@@ -214,7 +217,7 @@ vec3 convolution(mat3 kernel, vec2 filter_step)
 
     for (i = 0; i<3; ++i)
         for (j = 0; j<3; ++j)
-            sum += texture(iChannel0, vertexUV + filter_step * vec2 (i-1, j-1) ).rgb * kernel[i][j];
+            sum += texture(iChannel0, texcoord + filter_step * vec2 (i-1, j-1) ).rgb * kernel[i][j];
 
     return sum;
 }
@@ -224,7 +227,7 @@ vec3 apply_filter() {
     vec2 filter_step = 1.f / textureSize(iChannel0, 0);
 
     if (filterid < 1 || filterid > 11)
-        return texture(iChannel0, vertexUV).rgb;
+        return texture(iChannel0, texcoord).rgb;
     else if (filterid < 5)
         return convolution( KERNEL[filterid], filter_step);
     else if (filterid < 6)
@@ -313,10 +316,12 @@ float alphachromakey(vec3 color, vec3 colorKey, float delta)
 
 void main(void)
 {
+    // adjust UV
+    texcoord = vec2(uv.x, uv.y) + vertexUV * vec2(uv.z - uv.x, uv.w - uv.y);
 
     // deal with alpha separately
-    float ma = texture(iChannel0, vertexUV).a;
-//    float ma = texture(maskTexture, vertexUV).a * texture(iChannel0, vertexUV).a;
+    float ma = texture(iChannel0, texcoord).a;
+//    float ma = texture(maskTexture, texcoord).a * texture(iChannel0, texcoord).a;
     float alpha = clamp(ma * color.a, 0.0, 1.0);
 
     // read color & apply basic filterid
diff --git a/rsc/shaders/simple.fs b/rsc/shaders/simple.fs
index 3beb9f1..f1bd6b0 100644
--- a/rsc/shaders/simple.fs
+++ b/rsc/shaders/simple.fs
@@ -4,9 +4,11 @@ out vec4 FragColor;
 
 in vec4 vertexColor;
 
-uniform vec4 color;            // drawing color
 uniform vec3 iResolution;      // viewport resolution (in pixels)
 
+uniform vec4 color;            // drawing color
+uniform vec4 uv;
+
 void main()
 {
     FragColor = color * vertexColor;