konva/src/filters/Crop.js

(function(Kinetic) {

	function pixelAt(idata, x, y) {
		var idx = (y * idata.width + x) * 4;
		var d = [];
		d.push(idata.data[idx++], idata.data[idx++], idata.data[idx++], idata.data[idx++]);
		return d;
	};

	function rgbDistance(p1, p2) {
		return Math.sqrt(Math.pow(p1[0] - p2[0], 2) + Math.pow(p1[1] - p2[1], 2) + Math.pow(p1[2] - p2[2], 2));
	};

	function rgbMean(pTab) {
		var m = [0, 0, 0];

		for (var i = 0; i < pTab.length; i++) {
			m[0] += pTab[i][0];
			m[1] += pTab[i][1];
			m[2] += pTab[i][2];
		}

		m[0] /= pTab.length;
		m[1] /= pTab.length;
		m[2] /= pTab.length;

		return m;
	};

	function backgroundMask(idata, config) {
		var rgbv_no = pixelAt(idata, 0, 0);
		var rgbv_ne = pixelAt(idata, idata.width - 1, 0);
		var rgbv_so = pixelAt(idata, 0, idata.height - 1);
		var rgbv_se = pixelAt(idata, idata.width - 1, idata.height - 1);


		var thres = (config && config.threshold) ? config.threshold : 10;
		if (rgbDistance(rgbv_no, rgbv_ne) < thres && rgbDistance(rgbv_ne, rgbv_se) < thres && rgbDistance(rgbv_se, rgbv_so) < thres && rgbDistance(rgbv_so, rgbv_no) < thres) {

			// Mean color
			var mean = rgbMean([rgbv_ne, rgbv_no, rgbv_se, rgbv_so]);

			// Mask based on color distance
			var mask = [];
			for (var i = 0; i < idata.width * idata.height; i++) {
				var d = rgbDistance(mean, [idata.data[i * 4], idata.data[i * 4 + 1], idata.data[i * 4 + 2]]);
				mask[i] = (d < thres) ? 0 : 255;
			}

			return mask;
		}
	};

	function applyMask(idata, mask) {
		for (var i = 0; i < idata.width * idata.height; i++) {
			idata.data[4 * i + 3] = mask[i];
		}
	};

	function erodeMask(mask, sw, sh) {

		var weights = [1, 1, 1, 1, 0, 1, 1, 1, 1];
		var side = Math.round(Math.sqrt(weights.length));
		var halfSide = Math.floor(side / 2);

		var maskResult = [];
		for (var y = 0; y < sh; y++) {
			for (var x = 0; x < sw; x++) {

				var so = y * sw + x;
				var a = 0;
				for (var cy = 0; cy < side; cy++) {
					for (var cx = 0; cx < side; cx++) {
						var scy = y + cy - halfSide;
						var scx = x + cx - halfSide;

						if (scy >= 0 && scy < sh && scx >= 0 && scx < sw) {

							var srcOff = scy * sw + scx;
							var wt = weights[cy * side + cx];

							a += mask[srcOff] * wt;
						}
					}
				}

				maskResult[so] = (a === 255 * 8) ? 255 : 0;
			}
		}

		return maskResult;
	};

	function dilateMask(mask, sw, sh) {

		var weights = [1, 1, 1, 1, 1, 1, 1, 1, 1];
		var side = Math.round(Math.sqrt(weights.length));
		var halfSide = Math.floor(side / 2);

		var maskResult = [];
		for (var y = 0; y < sh; y++) {
			for (var x = 0; x < sw; x++) {

				var so = y * sw + x;
				var a = 0;
				for (var cy = 0; cy < side; cy++) {
					for (var cx = 0; cx < side; cx++) {
						var scy = y + cy - halfSide;
						var scx = x + cx - halfSide;

						if (scy >= 0 && scy < sh && scx >= 0 && scx < sw) {

							var srcOff = scy * sw + scx;
							var wt = weights[cy * side + cx];

							a += mask[srcOff] * wt;
						}
					}
				}

				maskResult[so] = (a >= 255 * 4) ? 255 : 0;
			}
		}

		return maskResult;
	};

	function smoothEdgeMask(mask, sw, sh) {

		var weights = [1 / 9, 1 / 9, 1 / 9, 1 / 9, 1 / 9, 1 / 9, 1 / 9, 1 / 9, 1 / 9];
		var side = Math.round(Math.sqrt(weights.length));
		var halfSide = Math.floor(side / 2);

		var maskResult = [];
		for (var y = 0; y < sh; y++) {
			for (var x = 0; x < sw; x++) {

				var so = y * sw + x;
				var a = 0;
				for (var cy = 0; cy < side; cy++) {
					for (var cx = 0; cx < side; cx++) {
						var scy = y + cy - halfSide;
						var scx = x + cx - halfSide;

						if (scy >= 0 && scy < sh && scx >= 0 && scx < sw) {

							var srcOff = scy * sw + scx;
							var wt = weights[cy * side + cx];

							a += mask[srcOff] * wt;
						}
					}
				}

				maskResult[so] = a;
			}
		}

		return maskResult;
	}
	
	Kinetic = Kinetic || {};
	Kinetic.Filters = Kinetic.Filters || {};

	/**
	 * Crop Filter
	 *
	 * Only crop unicolor background images for instance
	 *
	 * @function
	 * @memberOf Kinetic.Filters
	 * @param {Object} imageData
	 * @param {Object} config
	 * @param {Integer} config.threshold The RGB euclidian distance threshold (default : 10) 
	 */
	Kinetic.Filters.Crop = function(idata, config) {
		// Detect pixels close to the background color
		var mask = backgroundMask(idata, config);
		if (mask) {
			// Erode
			mask = erodeMask(mask, idata.width, idata.height);

			// Dilate
			mask = dilateMask(mask, idata.width, idata.height);

			// Gradient
			mask = smoothEdgeMask(mask, idata.width, idata.height);

			// Apply mask
			applyMask(idata, mask);
			
			// todo : Update hit region function according to mask
		}

		return idata;
	};

	window['Kinetic'] = Kinetic;

})(Kinetic);