如何在字节数组中缩放 RGB 图像的宽度

Question

My brain is not working properly today and I can't seem to figure this out.

I have a RGBA image data stored in an Uint8Array() and need to scale the width only.

var w = 160;
var h = 200;
var depth=4;
var pixels = new Uint8Array(w*h*depth);

I need to scale the pixels array to 320x200 and every attempt I did ended up with a garbled image.

Answer 1

Thanks to Yves Daoust I revisited some of my old attempts at solving this by duplicating every chunk of 4 to the destination, and now I got it working. So thank you Yves :) I do not know what I did wrong earlier.

This is the working code that I ended up with. I'm 100% sure it can be done differently and better, but at this point I am satisfied :)

Utils.prototype.scalePixelsInWidth = function(pixels) {

  var w = 320;
  var h = 200;
  var scanlineWidth = w*4;
  var scaledPixels = new Uint8Array(w*h*4);

  var a = 0;
  for(let row=0;row<h;row++) {
    var col2 = 0;
    for(let col=0;col<w;col++) {
      var srcIndex = col2*4 + (row*(w/2)*4);
      var destIndex = col*4 + (row * scanlineWidth);
      scaledPixels[destIndex+0] = pixels[srcIndex+0];
      scaledPixels[destIndex+1] = pixels[srcIndex+1];
      scaledPixels[destIndex+2] = pixels[srcIndex+2];
      scaledPixels[destIndex+3] = pixels[srcIndex+3];
      a++;
      if (a > 1) {
        a = 0;
        col2++;
      }
    }
  }

  return scaledPixels;

}