canvasfilters-extra-filters.js

// Extra filters for https://github.com/kig/canvasfilters.git


Filters.scaleUp = function (imageData, scale = 2) {
  const sourceWidth = imageData.width;
  const sourceHeight = imageData.height;

  const targetWidth = parseInt(sourceWidth * scale, 10);
  const targetHeight = parseInt(sourceHeight * scale, 10);

  const targetImageData = new ImageData(targetWidth, targetHeight);

  for (let row = 0; row < sourceHeight; row++) {
    for (let col = 0; col < sourceWidth; col++) {
      const sourcePixel = [
        imageData.data[(row * sourceWidth + col) * 4 + 0],
        imageData.data[(row * sourceWidth + col) * 4 + 1],
        imageData.data[(row * sourceWidth + col) * 4 + 2],
        imageData.data[(row * sourceWidth + col) * 4 + 3]
      ];
      for (let y = 0; y < scale; y++) {
        const destRow = row * scale + y;
        for (let x = 0; x < scale; x++) {
          const destCol = col * scale + x;
          for (let i = 0; i < 4; i++) {
            targetImageData.data[(destRow * targetImageData.width + destCol) * 4 + i]
              = sourcePixel[i];
          }
        }
      }
    }
  }

  return targetImageData;
};


Filters.sharpen = function(imageData, sharpenLevel) {
  // inspired by https://gist.github.com/mikecao/65d9fc92dc7197cb8a7c
  var mix = sharpenLevel || 0.3; // sharpen level. 0 - 1
  var w = imageData.width;
  var h = imageData.height;

  var x, sx, sy, r, g, b, a, dstOff, srcOff, wt, cx, cy, scy, scx,
    weights = [0, -1, 0, -1, 5, -1, 0, -1, 0],
    katet = Math.round(Math.sqrt(weights.length)),
    half = (katet * 0.5) | 0,
    dstData = new ImageData(w, h),
    dstBuff = dstData.data,
    srcBuff = imageData.data,
    y = h;

  while (y--) {
    x = w;
    while (x--) {
      sy = y;
      sx = x;
      dstOff = (y * w + x) * 4;
      r = 0;
      g = 0;
      b = 0;
      a = 0;

      for (cy = 0; cy < katet; cy++) {
        for (cx = 0; cx < katet; cx++) {
          scy = sy + cy - half;
          scx = sx + cx - half;

          if (scy >= 0 && scy < h && scx >= 0 && scx < w) {
            srcOff = (scy * w + scx) * 4;
            wt = weights[cy * katet + cx];

            r += srcBuff[srcOff] * wt;
            g += srcBuff[srcOff + 1] * wt;
            b += srcBuff[srcOff + 2] * wt;
            a += srcBuff[srcOff + 3] * wt;
          }
        }
      }

      dstBuff[dstOff] = r * mix + srcBuff[dstOff] * (1 - mix);
      dstBuff[dstOff + 1] = g * mix + srcBuff[dstOff + 1] * (1 - mix);
      dstBuff[dstOff + 2] = b * mix + srcBuff[dstOff + 2] * (1 - mix);
      dstBuff[dstOff + 3] = srcBuff[dstOff + 3];
    }
  }

  return dstData;
};