How to scale an imageData in HTML canvas?

Question

I have a canvas in my webpage; I create a new Image data in this canvas then I modify some pixel through myImgData.data[] array. Now I would like to scale this image and mak

Answer 1

I needed to do it without the interpolation that putImageData() causes, so I did it by scaling the image data into a new, resized ImageData object. I can't think of any other time I've thought that using 5 nested for loops was a good idea:

function scaleImageData(imageData, scale) {
  var scaled = c.createImageData(imageData.width * scale, imageData.height * scale);

  for(var row = 0; row < imageData.height; row++) {
    for(var col = 0; col < imageData.width; col++) {
      var sourcePixel = [
        imageData.data[(row * imageData.width + col) * 4 + 0],
        imageData.data[(row * imageData.width + col) * 4 + 1],
        imageData.data[(row * imageData.width + col) * 4 + 2],
        imageData.data[(row * imageData.width + col) * 4 + 3]
      ];
      for(var y = 0; y < scale; y++) {
        var destRow = row * scale + y;
        for(var x = 0; x < scale; x++) {
          var destCol = col * scale + x;
          for(var i = 0; i < 4; i++) {
            scaled.data[(destRow * scaled.width + destCol) * 4 + i] =
              sourcePixel[i];
          }
        }
      }
    }
  }

  return scaled;
}

I hope that at least one other programmer can copy and paste this into their editor while muttering, "There but for the grace of god go I."