如何使用GPUImage实现GPUImageMaskFilter [英] How to Implement GPUImageMaskFilter using GPUImage
问题描述
我需要使用蒙版从完整图像剪切并创建蒙版图像。
I need to Cut from the Full Image using the mask and created the masked Image.
+ =
我尝试了以下内容：
UIImage *imgMask = [UIImage imageNamed:@"Mask.png"];
UIImage *imgBgImage = [UIImage imageNamed:@"Full.png"];
GPUImageMaskFilter *maskingFilter = [[GPUImageMaskFilter alloc] init];
GPUImagePicture * maskGpuImage = [[GPUImagePicture alloc] initWithImage:imgMask ];
GPUImagePicture *FullGpuImage = [[GPUImagePicture alloc] initWithImage:imgBgImage ];
[maskGpuImage addTarget:maskingFilter];
[maskGpuImage processImage];
[maskingFilter useNextFrameForImageCapture];
[FullGpuImage addTarget:maskingFilter];
[FullGpuImage processImage];
UIImage *OutputImage = [maskingFilter imageFromCurrentFramebuffer];
但是，我生成的输出图像是：
But , my generated output image is:
请大家一起携手。
干杯。
Please guys join hands. Cheers.
此外，感谢 BradLarson 。
推荐答案
掩码是第二个目标，如过滤器中所示着色器代码（textureColor2）。
The mask is the second target, as can been seen in the filter shader code (textureColor2).
//Averages mask's the RGB values, and scales that value by the mask's alpha
//
//The dot product should take fewer cycles than doing an average normally
//
//Typical/ideal case, R,G, and B will be the same, and Alpha will be 1.0
lowp float newAlpha = dot(textureColor2.rgb, vec3(.33333334, .33333334, .33333334)) * textureColor2.a;
gl_FragColor = vec4(textureColor.xyz, newAlpha);
然后你需要反转你的面具：黑色背景上的白心，因为过滤器使用的是RGB像素值的权重，用于设置目标图像上的alpha值。
Then you need to "invert" your mask : white heart on black background, as the filter uses the "weight" of the RGB pixel value to set the alpha value on the target image.
所以你的代码应该是
// Image first, Mask next
[FullGpuImage addTarget:maskingFilter];
[FullGpuImage processImage];
[maskingFilter useNextFrameForImageCapture];
[maskGpuImage addTarget:maskingFilter];
[maskGpuImage processImage];
和你的面具（好吧，我做了一个丑陋的快速测试，使用正确的图像），如
and your mask (ok I did an ugly quick test, use a proper image) like
预期结果。
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