Adding simple filters to ChromeOS Image Editor.

chrome/browser/resources/file_manager/js/image_editor/filter.js

Index: chrome/browser/resources/file_manager/js/image_editor/filter.js
diff --git a/chrome/browser/resources/file_manager/js/image_editor/filter.js b/chrome/browser/resources/file_manager/js/image_editor/filter.js
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+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+/**
+ * A namespace class for image filter utilities.
+ */
+function Filter() {}
+
+/**
+ * Create a filter from name and options.
+ *
+ * @param {String} name Maps to a Filter method name.

[SeRya, 2011/08/10 13:00:20]

Shouldn't it be "@param {string}" ?

[Vladislav Kaznacheev, 2011/08/10 14:03:25]

Done.

+ * @param {Object} options A map of filter-specific options.
+ * @return {Function} A closure to be called with 4 parameters:

[SeRya, 2011/08/10 13:00:20]

@return {function(ImageData,ImageData,umber,number):void} ?

[Vladislav Kaznacheev, 2011/08/10 14:03:25]

Done.

+ *                    filter(dstImageData, srcImageData, offsetX, offsetY)
+ */
+Filter.create = function(name, options) {
+  var filter = Filter[name](options);
+  return function() {
+    var time = Date.now();
+    filter.apply(null, arguments);
+    var dst = arguments[0];
+    var mPixPerSec = dst.width * dst.height / 1000 / (Date.now() - time);
+    ImageUtil.trace.report(name, Math.round(mPixPerSec * 10) / 10 + 'Mps');
+  }
+};
+
+/**
+ * Apply a filter to a image by splitting it into strips.
+ *
+ * To be used with large images to avoid freezing up the UI.
+ *
+ * @param {CanvasRenderingContext2D} context
+ * @param {Function} filterFunc
+ * @param {Function} progressCallback Called with 2 parameters (current, total).
+ * @param {Number} maxPixelsPerStrip

[SeRya, 2011/08/10 13:00:20]

{number}

[Vladislav Kaznacheev, 2011/08/10 14:03:25]

Done.

+ */
+Filter.applyByStrips = function(
+    context, filterFunc, progressCallback, maxPixelsPerStrip) {
+  var source = context.getImageData(
+      0, 0, context.canvas.width, context.canvas.height);
+
+  var stripCount = Math.ceil (source.width * source.height /
+      (maxPixelsPerStrip || 1000000));  // 1 Mpix is a reasonable default.
+
+  var strip = context.getImageData(0, 0,
+      source.width, Math.ceil (source.height / stripCount));
+
+  var offset = 0;
+
+  function filterStrip() {
+    // If the strip overlaps the bottom of the source image we cannot shrink it
+    // and we cannot fill it partially (since canvas.putImageData always draws
+    // the entire buffer).
+    // Instead we move the strip up several lines (converting those lines
+    // twice is a small price to pay).
+    if (offset > source.height - strip.height) {
+      offset = source.height - strip.height;
+    }
+
+    filterFunc(strip, source, 0, offset);
+    context.putImageData(strip, 0, offset);
+
+    offset += strip.height;
+    progressCallback(offset, source.height);
+
+    if (offset < source.height) {
+      setTimeout(filterStrip, 0);
+    }
+  }
+
+  filterStrip();
+};
+
+/**
+ * Return a color histogram for an image.
+ *
+ * @param {ImageData} imageData
+ */
+Filter.getHistogram = function(imageData) {
+  var r = [];
+  var g = [];
+  var b = [];
+
+  for (var i = 0; i != 256; i++) {
+    r.push(0);
+    g.push(0);
+    b.push(0);
+  }
+
+  var data = imageData.data;
+  var maxIndex = 4 * imageData.width * imageData.height;
+  for (var index = 0; index != maxIndex;) {
+    r[data[index++]]++;
+    g[data[index++]]++;
+    b[data[index++]]++;
+    index++;
+  }
+
+  return { r: r, g: g, b: b };
+};
+
+/**
+ * Compute the function for every integer value from 0 up to maxArg.
+ *
+ * Rounds and clips the results to fit the [0..255] range.
+ * Useful to speed up pixel manipulations.
+ *
+ * @param {Number} maxArg Maximum argument value (inclusive).
+ * @param {Function} func Function returning a number.
+ * @return {Array<Number>} Computed results
+ */
+Filter.precompute = function(maxArg, func) {
+  var results = [];
+  for (var arg = 0; arg <= maxArg; arg ++) {
+    results.push(Math.max(0, Math.min(0xFF, Math.round(func(arg)))));
+  }
+  return results;
+};
+
+/**
+ * Convert pixels by applying conversion tables to each channel individually.
+ *
+ * @param {Array<Number>} rMap Red channel conversion table.
+ * @param {Array<Number>} gMap Green channel conversion table.
+ * @param {Array<Number>} bMap Blue channel conversion table.
+ * @param {ImageData} dst Destination image data. Can be smaller than the
+ *                        source, must completely fit inside the source.
+ * @param {ImageData} src Source image data.
+ * @param {Number} offsetX Horizontal offset of dst relative to src.
+ * @param {Number} offsetY Vertical offset of dst relative to src.
+ */
+Filter.mapPixels = function(rMap, gMap, bMap, dst, src, offsetX, offsetY) {
+  var dstData = dst.data;
+  var dstWidth = dst.width;
+  var dstHeight = dst.height;
+
+  var srcData = src.data;
+  var srcWidth = src.width;
+  var srcHeight = src.height;
+
+  if (offsetX < 0 || offsetX + dstWidth > srcWidth ||
+      offsetY < 0 || offsetY + dstHeight > srcHeight)
+      throw new Error('Invalid offset');
+
+  var dstIndex = 0;
+  for (var y = 0; y != dstHeight; y++) {
+    var srcIndex = (offsetX + (offsetY + y)* srcWidth)* 4;
+    for (var x = 0; x != dstWidth; x++ ) {
+      dstData[dstIndex++] = rMap[srcData[srcIndex++]];
+      dstData[dstIndex++] = gMap[srcData[srcIndex++]];
+      dstData[dstIndex++] = bMap[srcData[srcIndex++]];
+      dstIndex++;
+      srcIndex++;
+    }
+  }
+};
+
+Filter.FIXED_POINT_SHIFT = 16;
+
+Filter.floatToFixedPoint = function(x) {
+  return Math.round(x * (1<< Filter.FIXED_POINT_SHIFT));
+};
+
+/**
+ * Perform an image convolution with a symmetrical 5x5 matrix:
+ *
+ *  0  0 w3  0  0
+ *  0 w2 w1 w2  0
+ * w3 w1 w0 w1 w3
+ *  0 w2 w1 w2  0
+ *  0  0 w3  0  0
+ *
+ * For performance reasons the weights are in fixed point format
+ * (left shifted by Filter.FIXED_POINT_SHIFT).
+ *
+ * @param {Number} w0 See the picture above
+ * @param {Number} w1 See the picture above
+ * @param {Number} w2 See the picture above
+ * @param {Number} w3 See the picture above
+ * @param {ImageData} dst Destination image data. Can be smaller than the
+ *                        source, must completely fit inside the source.
+ * @param {ImageData} src Source image data.
+ * @param {Number} offsetX Horizontal offset of dst relative to src.
+ * @param {Number} offsetY Vertical offset of dst relative to src.
+ */
+Filter.convolve5x5 = function(w0, w1, w2, w3, dst, src, offsetX, offsetY) {
+  var dstData = dst.data;
+  var dstWidth = dst.width;
+  var dstHeight = dst.height;
+  var dstStride = dstWidth * 4;
+
+  var srcData = src.data;
+  var srcWidth = src.width;
+  var srcHeight = src.height;
+  var srcStride = srcWidth * 4;
+  var srcStride2 = srcStride * 2;
+
+  if (offsetX < 0 || offsetX + dstWidth > srcWidth ||
+      offsetY < 0 || offsetY + dstHeight > srcHeight)
+      throw new Error('Invalid offset');
+
+  w0 = w0 || 0;
+  w1 = w1 || 0;
+  w2 = w2 || 0;
+  w3 = w3 || 0;
+
+  var margin = 2;
+
+  var startX = Math.max(0, margin - offsetX);
+  var endX = Math.min(dstWidth, srcWidth - margin - offsetX);
+
+  var startY = Math.max(0, margin - offsetY);
+  var endY = Math.min(dstHeight, srcHeight - margin - offsetY);
+
+  for (var y = startY; y != endY; y++) {
+    var dstIndex = y * dstStride + startX * 4;
+    var srcIndex = (y + offsetY) * srcStride + (startX + offsetX) * 4;
+
+    for (var x = startX; x != endX; x++ ) {
+      for (var c = 0; c != 3; c++) {
+        var sum = w0 * srcData[srcIndex] +
+                  w1 * (srcData[srcIndex - 4] +
+                        srcData[srcIndex + 4] +
+                        srcData[srcIndex - srcStride] +
+                        srcData[srcIndex + srcStride]) +
+                  w2 * (srcData[srcIndex - srcStride - 4] +
+                        srcData[srcIndex + srcStride - 4] +
+                        srcData[srcIndex - srcStride + 4] +
+                        srcData[srcIndex + srcStride + 4]) +
+                  w3 * (srcData[srcIndex - 8] +
+                        srcData[srcIndex + 8] +
+                        srcData[srcIndex - srcStride2] +
+                        srcData[srcIndex + srcStride2]);
+        if (sum < 0)
+          dstData[dstIndex++] = 0;
+        else if (sum > (0xFF << Filter.FIXED_POINT_SHIFT))
+          dstData[dstIndex++] = 0xFF;
+        else
+          dstData[dstIndex++] = sum >> Filter.FIXED_POINT_SHIFT;
+        srcIndex++;
+      }
+      srcIndex++;
+      dstIndex++;
+    }
+  }
+};
+
+/**
+ * Return a convolution filter function bound to specific weights.
+ *
+ * @param {Array<Number>} weights Weights for the convolution matrix.
+ * @return {Function}
+ */
+Filter.convolution5x5 = function(weights) {
+  var total = 0;
+  for (var i = 0; i != weights.length; i++)
+    total += weights[i] * (i ? 4 : 1);
+
+  for (i = 0; i != weights.length; i++) {
+    weights[i] = Filter.floatToFixedPoint(weights[i] / total);
+  }
+
+  return Filter.convolve5x5.bind(
+      null, weights[0], weights[1], weights[2], weights[3]);
+};
+
+/**
+ * Return a blur filter.
+ * @param {Object} options
+ * @return {Function}
+ */
+Filter.blur = function(options) {
+  if (options.radius == 1)
+    return Filter.convolution5x5(
+        [1, options.strength]);
+  else if (options.radius == 2)
+    return Filter.convolution5x5(
+        [1, options.strength, options.strength]);
+  else
+    return Filter.convolution5x5(
+        [1, options.strength, options.strength, options.strength]);
+};
+
+/**
+ * Return a sharpen filter.
+ * @param {Object} options
+ * @return {Function}
+ */
+Filter.sharpen = function(options) {
+  if (options.radius == 1)
+    return Filter.convolution5x5(
+        [5, -options.strength]);
+  else if (options.radius == 2)
+    return Filter.convolution5x5(
+        [10, -options.strength, -options.strength]);
+  else
+    return Filter.convolution5x5(
+        [15, -options.strength, -options.strength, -options.strength]);
+};
+
+/**
+ * Return an exposure filter.
+ * @param {Object} options
+ * @return {Function}
+ */
+Filter.exposure = function(options) {
+  var pixelMap = Filter.precompute(
+    255,
+    function(value) {
+     if (options.brightness > 0) {
+       value *= (1 + options.brightness);
+     } else {
+       value += (0xFF - value) * options.brightness;
+     }
+     return 0x80 +
+         (value - 0x80) * Math.tan((options.contrast + 1) * Math.PI / 4);
+    });
+
+  return Filter.mapPixels.bind(null, pixelMap, pixelMap, pixelMap);
+};
+
+/**
+ * Return a color autofix filter.
+ * @param {Object} options
+ * @return {Function}
+ */
+Filter.autofix = function(options) {
+  return Filter.mapPixels.bind(null,
+      Filter.autofix.stretchColors(options.histogram.r),
+      Filter.autofix.stretchColors(options.histogram.g),
+      Filter.autofix.stretchColors(options.histogram.b));
+};
+
+/**
+ * Return a conversion table that stretches the range of colors used
+ * in the image to 0..255.
+ * @param {Array<Number>} channelHistogram
+ * @return {Array<Number>}
+ */
+Filter.autofix.stretchColors = function(channelHistogram) {
+  var first = 0;
+  while (first <= 255 && channelHistogram[first] == 0)
+    first++;
+
+  var last = 255;
+  while (last > first && channelHistogram[last] == 0)
+    last--;
+
+  return Filter.precompute(
+      255,
+      last == first ?
+          function(x) { return x } :
+          function(x) { return (x - first) / (last - first) * 255 }
+  );
+};