图像梯度计算-compute image gradient

运行在GPU上面，大大加速的处理速度。这里，给大家做个演示。下图是演示结果，输入图像

大小为1920x1080，在我的上网本上面（显卡为HD 3200）能够达到10多帧每秒。

源代码如下：

代码 <?xml version="1.0" encoding="utf-8"?>
<graph name = "SobelEdgeDetection" xmlns="http://ns.adobe.com/PixelBenderGraph/1.0">
    <metadata name = "namespace" value =  "Image Processing"/>
    <metadata name = "vendor" value = "Terry" />
    <metadata name = "version" type = "int" value = "1" />

    <!-- Image inputs and outputs of the graph -->
    <inputImage type = "image4" name = "src" />
    <outputImage type = "image4" name = "dst" />
 
     <!-- Embedded kernel -->
      <kernel>
      <![CDATA[ 
         <languageVersion : 1.0;>
         kernel Gray 
         <   
            namespace:"Image Processing";
            vendor:"Terry";
            version:1;
         >
         {
            input image4 src;
            output float4 dst;

            void evaluatePixel()
            {
                float4 color = sample(src, outCoord());
                float gray = color.x*0.212671 + 0.715160*color.y + 0.072169*color.z;
                dst.xyz = float3(gray, gray, gray);
                dst.w = 1.0;
                
            }
         }
      ]]>
     </kernel>
     
      <!-- Embedded kernel -->
      <kernel>
      <![CDATA[ 
         <languageVersion : 1.0;>
         kernel Dx 
         <   
            namespace:"Image Processing";
            vendor:"Terry";
            version:1;
         >
         {
            input image4 src;
            output float4 dst;

            void evaluatePixel()
            {
                float3 dx = sampleNearest(src, outCoord() + float2(1.0, 0.0)).rgb - sampleNearest(src, outCoord() + float2(-1.0,0.0)).rgb;
                dst.xyz = dx;
                dst.w = 1.0;
                
            }
         }
      ]]>
     </kernel>
     
      <kernel>
      <![CDATA[ 
         <languageVersion : 1.0;>
         kernel Dy 
         <   
            namespace:"Image Processing";
            vendor:"Terry";
            version:1;
         >
         {
            input image4 src;
            output float4 dst;

            void evaluatePixel()
            {
                float3 dy = sampleNearest(src, outCoord() + float2(0.0, 1.0)).rgb - sampleNearest(src, outCoord() + float2(0.0,-1.0)).rgb;
                dst.xyz = dy;
                dst.w = 1.0;
                
            }
         }
      ]]>
     </kernel>
     
      <kernel>
      <![CDATA[ 
         <languageVersion : 1.0;>
         kernel SquareRoot 
         <   
            namespace:"Image Processing";
            vendor:"Terry";
            version:1;
         >
         {
            input image4 src1;
            input image4 src2;
            output float4 dst;

            void evaluatePixel()
            {
                float squareRoot = sqrt(sampleNearest(src1, outCoord()).r*sampleNearest(src1, outCoord()).r + 
                                        sampleNearest(src2, outCoord()).r*sampleNearest(src2, outCoord()).r);
                dst.xyz = float3(squareRoot, squareRoot, squareRoot);
                dst.w = 1.0;
                
            }
         }
      ]]>
     </kernel>

    <!-- Instances of the nodes -->
    <node id = "gray1" name ="Gray" namespace = "Image Processing" vendor = "Terry" version ="1" >
    </node>
    <node id = "dx1" name ="Dx" namespace = "Image Processing" vendor = "Terry" version ="1" >
    </node>
    <node id = "dy1" name ="Dy" namespace = "Image Processing" vendor = "Terry" version ="1" >
    </node>
    <node id = "squareRoot1" name ="SquareRoot" namespace = "Image Processing" vendor = "Terry" version ="1" >
    </node>

    <!-- Connect the graph -->
    <connect fromImage = "src" toNode = "gray1" toInput = "src" />
    <connect fromNode="gray1" fromOutput="dst" toNode="dx1" toInput="src"/>
    <connect fromNode="gray1" fromOutput="dst" toNode="dy1" toInput="src"/>
    <connect fromNode="dx1" fromOutput="dst" toNode="squareRoot1" toInput="src1"/>
    <connect fromNode="dy1" fromOutput="dst" toNode="squareRoot1" toInput="src2"/>
    <connect fromNode = "squareRoot1" fromOutput = "dst" toImage = "dst" />
</graph>