Initial commit

lib/assets/javascripts/signature_pad-extensions.js

@@ -0,0 +1,48 @@
+/**
+ * Crop signature canvas to only contain the signature and no whitespace.
+ *
+ * @returns The cropped canvas
+ * @credit - https://github.com/szimek/signature_pad/issues/49#issuecomment-260976909
+ */
+SignaturePad.prototype.crop = function() {
+  var canvas = this._ctx.canvas;
+
+	// First duplicate the canvas to not alter the original
+	var croppedCanvas = document.createElement('canvas'),
+	croppedCtx    = croppedCanvas.getContext('2d');
+
+	croppedCanvas.width  = canvas.width;
+	croppedCanvas.height = canvas.height;
+	croppedCtx.drawImage(canvas, 0, 0);
+
+	// Next do the actual cropping
+	var w         = croppedCanvas.width,
+	h         = croppedCanvas.height,
+	pix       = {x:[], y:[]},
+	imageData = croppedCtx.getImageData(0,0,croppedCanvas.width,croppedCanvas.height),
+	x, y, index;
+
+	for (y = 0; y < h; y++) {
+		for (x = 0; x < w; x++) {
+			index = (y * w + x) * 4;
+			if (imageData.data[index+3] > 0) {
+				pix.x.push(x);
+				pix.y.push(y);
+
+			}
+		}
+	}
+	pix.x.sort(function(a,b){return a-b});
+	pix.y.sort(function(a,b){return a-b});
+	var n = pix.x.length-1;
+
+	w = pix.x[n] - pix.x[0];
+	h = pix.y[n] - pix.y[0];
+	var cut = croppedCtx.getImageData(pix.x[0], pix.y[0], w, h);
+
+	croppedCanvas.width = w;
+	croppedCanvas.height = h;
+	croppedCtx.putImageData(cut, 0, 0);
+
+	return croppedCanvas;
+};