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应用锐化工具可以快速聚焦模糊边缘，提高图像中某一部位的清晰度或者焦距程度，使图像特定区域的色彩更加鲜明。 在应用锐化工具时，若勾选器选项栏中的“对所有图层取样”复选框，则可对所有可见图层中的图像进行锐化。但一定要适度。锐化不是万能的，很容易使东西不真实。
在GPUImage中使用GPUImageSharpenFilter类来实现图像的锐化效果
片段着色
precision highp float; varying highp vec2 textureCoordinate; varying highp vec2 leftTextureCoordinate; varying highp vec2 rightTextureCoordinate; varying highp vec2 topTextureCoordinate; varying highp vec2 bottomTextureCoordinate; varying highp float centerMultiplier; varying highp float edgeMultiplier; uniform sampler2D inputImageTexture; void main() { mediump vec3 textureColor = texture2D(inputImageTexture, textureCoordinate).rgb; mediump vec3 leftTextureColor = texture2D(inputImageTexture, leftTextureCoordinate).rgb; mediump vec3 rightTextureColor = texture2D(inputImageTexture, rightTextureCoordinate).rgb; mediump vec3 topTextureColor = texture2D(inputImageTexture, topTextureCoordinate).rgb; mediump vec3 bottomTextureColor = texture2D(inputImageTexture, bottomTextureCoordinate).rgb; gl_FragColor = vec4((textureColor * centerMultiplier - (leftTextureColor * edgeMultiplier + rightTextureColor * edgeMultiplier + topTextureColor * edgeMultiplier + bottomTextureColor * edgeMultiplier)), texture2D(inputImageTexture, bottomTextureCoordinate).w); }
具体应用
+ (UIImage *)changeValueForSharpenilter:(float)value image:(UIImage *)image { GPUImageSharpenFilter *filter = [[GPUImageSharpenFilter alloc] init]; filter.sharpness = value; [filter forceProcessingAtSize:image.size]; GPUImagePicture *pic = [[GPUImagePicture alloc] initWithImage:image]; [pic addTarget:filter]; [pic processImage]; [filter useNextFrameForImageCapture]; return [filter imageFromCurrentFramebuffer]; }
效果
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原文地址：http://www.cnblogs.com/salam/p/5120032.html
