如何在FabricJS中编写卷积过滤器以进行边缘检测 [英] How to write a convolution filter for Edge detection in FabricJS
问题描述
我想在Fabricjs中编写卷积过滤器以进行边缘检测,但是矩阵不起作用.
这是矩阵(从
//加载图像var image = new Image();image.crossOrigin ='anonymous';image.onload =开始;image.src ="https://dl.dropboxusercontent.com/u/139992952/multple/sun.png";函数start(){//应用Sobel边缘检测//返回过滤后的画布的ImageDatavar grayscale = Filters.filterImage(Filters.grayscale,image);var vertical = Filters.convoluteFloat32(灰度,[-1,0,1,-2,0,2,-1,0,1]);var horizontal = Filters.convoluteFloat32(灰度,[-1,-2,-1,0、0、0,1,2,1]);var final_image = Filters.createImageData(vertical.width,vertical.height);对于(var i = 0; i< final_image.data.length; i + = 4){//将垂直渐变设为红色var v = Math.abs(vertical.data [i]);final_image.data [i] = v;//使水平渐变变为绿色var h = Math.abs(horizontal.data [i]);final_image.data [i + 1] = h;//并混合一些蓝色以达到美观final_image.data [i + 2] =(v + h)/4;final_image.data [i + 3] = 255;//不透明的Alpha}//将过滤后的imageData放在内存画布上var memCanvas = document.createElement('canvas');memCanvas.width = image.width;memCanvas.height = image.height;memCanvas.getContext('2d').putImageData(final_image,0,0);//将内存画布用作Fabric.Image的图像源var canvas = new fabric.Canvas('canvas');var imgElement = document.getElementById('my-image');var imgInstance = new fabric.Image(memCanvas,{left:10,top:10});canvas.add(imgInstance);}
body {background-color:ivory;}canvas {border:1px纯红色;margin:0自动;}
<脚本src ="https://dl.dropboxusercontent.com/u/139992952/multple/filters.js"><;/script>< script src ="http://cdnjs.cloudflare.com/ajax/libs/fabric.js/1.5.0/fabric.min.js"></script>< h4>原始图像</h4>< img src ='https://dl.dropboxusercontent.com/u/139992952/multple/sun.png'>< h4>应用了Sobel滤镜的FabricJS图像</h4>< canvas id ="canvas" width = 300 height = 200></canvas>
这是演示中使用的 Filters.js
脚本:
//出处:http://www.html5rocks.com/en/tutorials/canvas/imagefilters/过滤器= {};Filters.getPixels = function(img){var c,ctx;如果(img.getContext){c = img;尝试{ctx = c.getContext('2d');} catch(e){}}如果(!ctx){c = this.getCanvas(img.width,img.height);ctx = c.getContext('2d');ctx.drawImage(img,0,0);}返回ctx.getImageData(0,0,c.width,c.height);};Filters.getCanvas = function(w,h){var c = document.createElement('canvas');c.width = w;c.height = h;返回c;};Filters.filterImage = function(filter,image,var_args){var args = [this.getPixels(image)];for(var i = 2; i< arguments.length; i ++){args.push(arguments [i]);}返回filter.apply(null,args);};Filters.grayscale = function(pixels,args){var d = pixel.data;对于(var i = 0; i =阈值)255:0;d [i] = d [i + 1] = d [i + 2] = v}返回像素;};Filters.tmpCanvas = document.createElement('canvas');Filters.tmpCtx = Filters.tmpCanvas.getContext('2d');Filters.createImageData = function(w,h){返回this.tmpCtx.createImageData(w,h);};Filters.convolute =函数(像素,权重,不透明){var side = Math.round(Math.sqrt(weights.length));var halfSide = Math.floor(side/2);var src = pixel.data;var sw = pixel.width;var sh = pixel.height;var w = sw;var h = sh;var输出= Filters.createImageData(w,h);var dst = output.data;var alphaFac =不透明?1:0;对于(var y = 0; y< h; y ++){对于(var x = 0; x< w; x ++){var sy = y;var sx = x;var dstOff =(y * w + x)* 4;var r = 0,g = 0,b = 0,a = 0;for(var cy = 0; cy< side; cy ++){for(var cx = 0; cx< side; cx ++){var scy = Math.min(sh-1,Math.max(0,sy + cy-halfSide));var scx = Math.min(sw-1,Math.max(0,sx + cx-halfSide));var srcOff =(scy * sw + scx)* 4;var wt = weights [cy * side + cx];r + = src [srcOff] * wt;g + = src [srcOff + 1] * wt;b + = src [srcOff + 2] * wt;a + = src [srcOff + 3] * wt;}}dst [dstOff] = r;dst [dstOff + 1] = g;dst [dstOff + 2] = b;dst [dstOff + 3] = a + alphaFac *(255-a);}}返回输出;};如果(!window.Float32Array)Float32Array =数组;Filters.convoluteFloat32 =函数(像素,权重,不透明){var side = Math.round(Math.sqrt(weights.length));var halfSide = Math.floor(side/2);var src = pixel.data;var sw = pixel.width;var sh = pixel.height;var w = sw;var h = sh;var输出= {宽度:w,高度:h,数据:新的Float32Array(w * h * 4)};var dst = output.data;var alphaFac =不透明?1:0;对于(var y = 0; y< h; y ++){对于(var x = 0; x< w; x ++){var sy = y;var sx = x;var dstOff =(y * w + x)* 4;var r = 0,g = 0,b = 0,a = 0;for(var cy = 0; cy< side; cy ++){for(var cx = 0; cx< side; cx ++){var scy = Math.min(sh-1,Math.max(0,sy + cy-halfSide));var scx = Math.min(sw-1,Math.max(0,sx + cx-halfSide));var srcOff =(scy * sw + scx)* 4;var wt = weights [cy * side + cx];r + = src [srcOff] * wt;g + = src [srcOff + 1] * wt;b + = src [srcOff + 2] * wt;a + = src [srcOff + 3] * wt;}}dst [dstOff] = r;dst [dstOff + 1] = g;dst [dstOff + 2] = b;dst [dstOff + 3] = a + alphaFac *(255-a);}}返回输出;};//函数runFilter(id,filter,arg1,arg2,arg3){var c = document.getElementById(id);var s = c.previousSibling.style;var b = c.parentNode.getElementsByTagName('button')[0];如果(b.originalText == null){b.originalText = b.textContent;}如果(s.display =='none'){s.display ='inline';c.style.display ='none';b.textContent = b.originalText;} 别的 {var idata = Filters.filterImage(filter,img,arg1,arg2,arg3);c.width = idata.width;c.height = idata.height;var ctx = c.getContext('2d');ctx.putImageData(idata,0,0);s.display ='none';c.style.display ='inline';b.textContent ='恢复原始图像';}}//sobel = function(){runFilter('sobel',function(px){px = Filters.grayscale(px);var vertical = Filters.convoluteFloat32(px,[-1,-2,-1,0、0、0,1,2,1]);var horizontal = Filters.convoluteFloat32(px,[-1,0,1,-2,0,2,-1,0,1]);var id = Filters.createImageData(vertical.width,vertical.height);对于(var i = 0; i< id.data.length; i + = 4){var v = Math.abs(vertical.data [i]);id.data [i] = v;var h = Math.abs(horizontal.data [i]);id.data [i + 1] = hid.data [i + 2] =(v + h)/4;id.data [i + 3] = 255;}返回ID;});}
I want to write a convolution filter for edge detection in Fabricjs , but the matrix doesn't work.
Here's the Matrix (Idea taken from http://homepages.inf.ed.ac.uk/rbf/HIPR2/sobel.htm):
new fabric.Image.filters.Convolute({ // edge detect
matrix: [[ -1, 0, 1,
-2, 0, 2,
-1, 0, 1 ],
[1, 2, 1,
0 ,0 ,0,
-1, -2, 1 ]]
})
heres the Fiddle
NOTE:- You need to click on the image to get the check boxes for image processing.
Since a native html5 canvas element can be an image for Fabric.Image, you can find an Edge detection solution for native canvas and then use that native canvas on a Fabric.Image like this image:myNativeCanvas
.
[Addition: added a demo]
Here's example code and a demo showing how to:
- Use a native canvas to apply Sobel Edge Detection to an image and
- Use that native canvas as the image source for a Fabric.Image
// load an image
var image=new Image();
image.crossOrigin='anonymous';
image.onload=start;
image.src="https://dl.dropboxusercontent.com/u/139992952/multple/sun.png";
function start(){
// apply Sobel Edge Detection
// return ImageData of the filtered canvas
var grayscale = Filters.filterImage(Filters.grayscale, image);
var vertical = Filters.convoluteFloat32(grayscale,
[ -1, 0, 1,
-2, 0, 2,
-1, 0, 1 ]);
var horizontal = Filters.convoluteFloat32(grayscale,
[ -1, -2, -1,
0, 0, 0,
1, 2, 1 ]);
var final_image = Filters.createImageData(vertical.width, vertical.height);
for (var i=0; i<final_image.data.length; i+=4){
// make the vertical gradient red
var v = Math.abs(vertical.data[i]);
final_image.data[i] = v;
// make the horizontal gradient green
var h = Math.abs(horizontal.data[i]);
final_image.data[i+1] = h;
// and mix in some blue for aesthetics
final_image.data[i+2] = (v+h)/4;
final_image.data[i+3] = 255; // opaque alpha
}
// put the filtered imageData on an in-memory canvas
var memCanvas = document.createElement('canvas');
memCanvas.width=image.width;
memCanvas.height=image.height;
memCanvas.getContext('2d').putImageData(final_image,0,0);
// use the in-memory canvas as an image source for a Fabric.Image
var canvas = new fabric.Canvas('canvas');
var imgElement = document.getElementById('my-image');
var imgInstance = new fabric.Image(memCanvas,{left:10,top:10});
canvas.add(imgInstance);
}
body{ background-color: ivory; }
canvas{border:1px solid red; margin:0 auto; }
<script src="https://dl.dropboxusercontent.com/u/139992952/multple/filters.js"></script>
<script src="http://cdnjs.cloudflare.com/ajax/libs/fabric.js/1.5.0/fabric.min.js"></script>
<h4>Original Image</h4>
<img src='https://dl.dropboxusercontent.com/u/139992952/multple/sun.png'>
<h4>FabricJS image with Sobel filter applied</h4>
<canvas id="canvas" width=300 height=200></canvas>
And here is the Filters.js
script used in the demo:
// Attribution: http://www.html5rocks.com/en/tutorials/canvas/imagefilters/
Filters = {};
Filters.getPixels = function(img) {
var c,ctx;
if (img.getContext) {
c = img;
try { ctx = c.getContext('2d'); } catch(e) {}
}
if (!ctx) {
c = this.getCanvas(img.width, img.height);
ctx = c.getContext('2d');
ctx.drawImage(img, 0, 0);
}
return ctx.getImageData(0,0,c.width,c.height);
};
Filters.getCanvas = function(w,h) {
var c = document.createElement('canvas');
c.width = w;
c.height = h;
return c;
};
Filters.filterImage = function(filter, image, var_args) {
var args = [this.getPixels(image)];
for (var i=2; i<arguments.length; i++) {
args.push(arguments[i]);
}
return filter.apply(null, args);
};
Filters.grayscale = function(pixels, args) {
var d = pixels.data;
for (var i=0; i<d.length; i+=4) {
var r = d[i];
var g = d[i+1];
var b = d[i+2];
// CIE luminance for the RGB
var v = 0.2126*r + 0.7152*g + 0.0722*b;
d[i] = d[i+1] = d[i+2] = v
}
return pixels;
};
Filters.brightness = function(pixels, adjustment) {
var d = pixels.data;
for (var i=0; i<d.length; i+=4) {
d[i] += adjustment;
d[i+1] += adjustment;
d[i+2] += adjustment;
}
return pixels;
};
Filters.threshold = function(pixels, threshold) {
var d = pixels.data;
for (var i=0; i<d.length; i+=4) {
var r = d[i];
var g = d[i+1];
var b = d[i+2];
var v = (0.2126*r + 0.7152*g + 0.0722*b >= threshold) ? 255 : 0;
d[i] = d[i+1] = d[i+2] = v
}
return pixels;
};
Filters.tmpCanvas = document.createElement('canvas');
Filters.tmpCtx = Filters.tmpCanvas.getContext('2d');
Filters.createImageData = function(w,h) {
return this.tmpCtx.createImageData(w,h);
};
Filters.convolute = function(pixels, weights, opaque) {
var side = Math.round(Math.sqrt(weights.length));
var halfSide = Math.floor(side/2);
var src = pixels.data;
var sw = pixels.width;
var sh = pixels.height;
var w = sw;
var h = sh;
var output = Filters.createImageData(w, h);
var dst = output.data;
var alphaFac = opaque ? 1 : 0;
for (var y=0; y<h; y++) {
for (var x=0; x<w; x++) {
var sy = y;
var sx = x;
var dstOff = (y*w+x)*4;
var r=0, g=0, b=0, a=0;
for (var cy=0; cy<side; cy++) {
for (var cx=0; cx<side; cx++) {
var scy = Math.min(sh-1, Math.max(0, sy + cy - halfSide));
var scx = Math.min(sw-1, Math.max(0, sx + cx - halfSide));
var srcOff = (scy*sw+scx)*4;
var wt = weights[cy*side+cx];
r += src[srcOff] * wt;
g += src[srcOff+1] * wt;
b += src[srcOff+2] * wt;
a += src[srcOff+3] * wt;
}
}
dst[dstOff] = r;
dst[dstOff+1] = g;
dst[dstOff+2] = b;
dst[dstOff+3] = a + alphaFac*(255-a);
}
}
return output;
};
if (!window.Float32Array)
Float32Array = Array;
Filters.convoluteFloat32 = function(pixels, weights, opaque) {
var side = Math.round(Math.sqrt(weights.length));
var halfSide = Math.floor(side/2);
var src = pixels.data;
var sw = pixels.width;
var sh = pixels.height;
var w = sw;
var h = sh;
var output = {
width: w, height: h, data: new Float32Array(w*h*4)
};
var dst = output.data;
var alphaFac = opaque ? 1 : 0;
for (var y=0; y<h; y++) {
for (var x=0; x<w; x++) {
var sy = y;
var sx = x;
var dstOff = (y*w+x)*4;
var r=0, g=0, b=0, a=0;
for (var cy=0; cy<side; cy++) {
for (var cx=0; cx<side; cx++) {
var scy = Math.min(sh-1, Math.max(0, sy + cy - halfSide));
var scx = Math.min(sw-1, Math.max(0, sx + cx - halfSide));
var srcOff = (scy*sw+scx)*4;
var wt = weights[cy*side+cx];
r += src[srcOff] * wt;
g += src[srcOff+1] * wt;
b += src[srcOff+2] * wt;
a += src[srcOff+3] * wt;
}
}
dst[dstOff] = r;
dst[dstOff+1] = g;
dst[dstOff+2] = b;
dst[dstOff+3] = a + alphaFac*(255-a);
}
}
return output;
};
//
function runFilter(id, filter, arg1, arg2, arg3) {
var c = document.getElementById(id);
var s = c.previousSibling.style;
var b = c.parentNode.getElementsByTagName('button')[0];
if (b.originalText == null) {
b.originalText = b.textContent;
}
if (s.display == 'none') {
s.display = 'inline';
c.style.display = 'none';
b.textContent = b.originalText;
} else {
var idata = Filters.filterImage(filter, img, arg1, arg2, arg3);
c.width = idata.width;
c.height = idata.height;
var ctx = c.getContext('2d');
ctx.putImageData(idata, 0, 0);
s.display = 'none';
c.style.display = 'inline';
b.textContent = 'Restore original image';
}
}
//
sobel = function() {
runFilter('sobel', function(px){
px = Filters.grayscale(px);
var vertical = Filters.convoluteFloat32(px,
[-1,-2,-1,
0, 0, 0,
1, 2, 1]);
var horizontal = Filters.convoluteFloat32(px,
[-1,0,1,
-2,0,2,
-1,0,1]);
var id = Filters.createImageData(vertical.width, vertical.height);
for (var i=0; i<id.data.length; i+=4) {
var v = Math.abs(vertical.data[i]);
id.data[i] = v;
var h = Math.abs(horizontal.data[i]);
id.data[i+1] = h
id.data[i+2] = (v+h)/4;
id.data[i+3] = 255;
}
return id;
});
}
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