/******************************************************************************************/
//@Author:猿说编程
//@Blog(个人博客地址): www.codersrc.com
//@File:IOS – OpenGL ES GPUImage 图像显示亮度最高的像素,其他为黑 GPUImageNonMaximumSuppressionFilter
//@Time:2022/06/21 06:30
//@Motto:不积跬步无以至千里，不积小流无以成江海，程序人生的精彩需要坚持不懈地积累！
/******************************************************************************************/#if TARGET_IPHONE_SIMULATOR || TARGET_OS_IPHONE
NSString *const kGPUImageNonMaximumSuppressionFragmentShaderString = SHADER_STRING
(uniform sampler2D inputImageTexture;varying highp vec2 textureCoordinate;varying highp vec2 leftTextureCoordinate;varying highp vec2 rightTextureCoordinate;varying highp vec2 topTextureCoordinate;varying highp vec2 topLeftTextureCoordinate;varying highp vec2 topRightTextureCoordinate;varying highp vec2 bottomTextureCoordinate;varying highp vec2 bottomLeftTextureCoordinate;varying highp vec2 bottomRightTextureCoordinate;void main(){lowp float bottomColor = texture2D(inputImageTexture, bottomTextureCoordinate).r;lowp float bottomLeftColor = texture2D(inputImageTexture, bottomLeftTextureCoordinate).r;lowp float bottomRightColor = texture2D(inputImageTexture, bottomRightTextureCoordinate).r;lowp vec4 centerColor = texture2D(inputImageTexture, textureCoordinate);lowp float leftColor = texture2D(inputImageTexture, leftTextureCoordinate).r;lowp float rightColor = texture2D(inputImageTexture, rightTextureCoordinate).r;lowp float topColor = texture2D(inputImageTexture, topTextureCoordinate).r;lowp float topRightColor = texture2D(inputImageTexture, topRightTextureCoordinate).r;lowp float topLeftColor = texture2D(inputImageTexture, topLeftTextureCoordinate).r;// Use a tiebreaker for pixels to the left and immediately above this onelowp float multiplier = 1.0 - step(centerColor.r, topColor);multiplier = multiplier * (1.0 - step(centerColor.r, topLeftColor));multiplier = multiplier * (1.0 - step(centerColor.r, leftColor));multiplier = multiplier * (1.0 - step(centerColor.r, bottomLeftColor));lowp float maxValue = max(centerColor.r, bottomColor);maxValue = max(maxValue, bottomRightColor);maxValue = max(maxValue, rightColor);maxValue = max(maxValue, topRightColor);gl_FragColor = vec4((centerColor.rgb * step(maxValue, centerColor.r) * multiplier), 1.0);}
);
#else
NSString *const kGPUImageNonMaximumSuppressionFragmentShaderString = SHADER_STRING
(uniform sampler2D inputImageTexture;varying vec2 textureCoordinate;varying vec2 leftTextureCoordinate;varying vec2 rightTextureCoordinate;varying vec2 topTextureCoordinate;varying vec2 topLeftTextureCoordinate;varying vec2 topRightTextureCoordinate;varying vec2 bottomTextureCoordinate;varying vec2 bottomLeftTextureCoordinate;varying vec2 bottomRightTextureCoordinate;void main(){float bottomColor = texture2D(inputImageTexture, bottomTextureCoordinate).r;float bottomLeftColor = texture2D(inputImageTexture, bottomLeftTextureCoordinate).r;float bottomRightColor = texture2D(inputImageTexture, bottomRightTextureCoordinate).r;vec4 centerColor = texture2D(inputImageTexture, textureCoordinate);float leftColor = texture2D(inputImageTexture, leftTextureCoordinate).r;float rightColor = texture2D(inputImageTexture, rightTextureCoordinate).r;float topColor = texture2D(inputImageTexture, topTextureCoordinate).r;float topRightColor = texture2D(inputImageTexture, topRightTextureCoordinate).r;float topLeftColor = texture2D(inputImageTexture, topLeftTextureCoordinate).r;// Use a tiebreaker for pixels to the left and immediately above this onefloat multiplier = 1.0 - step(centerColor.r, topColor);multiplier = multiplier * (1.0 - step(centerColor.r, topLeftColor));multiplier = multiplier * (1.0 - step(centerColor.r, leftColor));multiplier = multiplier * (1.0 - step(centerColor.r, bottomLeftColor));float maxValue = max(centerColor.r, bottomColor);maxValue = max(maxValue, bottomRightColor);maxValue = max(maxValue, rightColor);maxValue = max(maxValue, topRightColor);gl_FragColor = vec4((centerColor.rgb * step(maxValue, centerColor.r) * multiplier), 1.0);}
);
#endif