added 2D version of invMatrix utility methods

core/src/processing/opengl/PGraphicsOpenGL.java

@@ -3772,6 +3772,13 @@ public class PGraphicsOpenGL extends PGraphics {
   }
 
 
+  static protected void invTranslate(PMatrix2D matrix,
+                                     float tx, float ty) {
+    matrix.preApply(1, 0, -tx,
+                    0, 1, -ty);
+  }
+
+
   static protected float matrixScale(PMatrix matrix) {
     // Volumetric scaling factor that is associated to the given
     // transformation matrix, which is given by the absolute value of its
@@ -3857,8 +3864,8 @@ public class PGraphicsOpenGL extends PGraphics {
   }
 
 
-  static private void invRotate(PMatrix3D matrix, float angle,
-                                float v0, float v1, float v2) {
+  static protected void invRotate(PMatrix3D matrix, float angle,
+                                  float v0, float v1, float v2) {
     float c = PApplet.cos(-angle);
     float s = PApplet.sin(-angle);
     float t = 1.0f - c;
@@ -3870,6 +3877,11 @@ public class PGraphicsOpenGL extends PGraphics {
   }
 
 
+  static protected void invRotate(PMatrix2D matrix, float angle) {
+    matrix.rotate(-angle);
+  }
+
+
   /**
    * Same as scale(s, s, s).
    */
@@ -3911,6 +3923,11 @@ public class PGraphicsOpenGL extends PGraphics {
   }
 
 
+  static protected void invScale(PMatrix2D matrix, float x, float y) {
+    matrix.preApply(1/x, 0, 0, 1/y, 0, 0);
+  }
+
+
   @Override
   public void shearX(float angle) {
     float t = (float) Math.tan(angle);