image-sequencer/src/modules/Crop.js

/*
 * Image Cropping module
 * Usage:
 *    Expected Inputs:
 *      options.x : x-coordinate of image where the modules starts cropping | default : 0
 *      options.y : y-coordinate of image where the modules starts cropping | default : 0
 *      options.w : width of the resulting cropped image | default : 50% of input image width
 *      options.h : height of the resulting cropped image | default : 50% of input image height
 *    Output:
 *      The cropped image, which is essentially a rectangle bounded by the lines:
 *          x = options.x
 *          x = options.x + options.w
 *          y = options.y
 *          y = options.y + options.h
 */
 module.exports = function Crop(options) {
   options = options || {};
   options.title = "Do Nothing";
   this_ = this;
   var output
   var getPixels = require("get-pixels"),
       savePixels = require("save-pixels"),
       base64 = require('base64-stream');

   function draw(input,callback) {

     const this_ = this;

     getPixels(input.src,function(err,pixels){
       var newdata = [];
       var ox = options.x || 0;
       var oy = options.y || 0;
       var w = options.w || Math.floor(0.5*pixels.shape[0]);
       var h = options.h || Math.floor(0.5*pixels.shape[1]);
       var iw = pixels.shape[0]; //Width of Original Image
       newarray = new Uint8Array(4*w*h);
       for (var n = oy; n < oy + h; n++) {
         newarray.set(pixels.data.slice(n*4*iw + ox, n*4*iw + ox + 4*w),4*w*(n-oy));
       }
       pixels.data = newarray;
       pixels.shape = [w,h,4];
       pixels.stride[1] = 4*w;

       options.format = "jpeg";

       w = base64.encode();
       var r = savePixels(pixels, options.format);
       r.pipe(w).on('finish',function(){
         data = w.read().toString();
         datauri = 'data:image/' + options.format + ';base64,' + data;
         this_.output = {src:datauri,format:options.format};
         callback();
       });
     });

   }

   return {
     options: options,
     draw: draw,
     output: output
   }
 }