Pods/GPUImage/framework/Source/GPUImageWeakPixelInclusionFilter.m
#import "GPUImageWeakPixelInclusionFilter.h"

@implementation GPUImageWeakPixelInclusionFilter

#if TARGET_IPHONE_SIMULATOR || TARGET_OS_IPHONE
NSString *const kGPUImageWeakPixelInclusionFragmentShaderString = SHADER_STRING
(
 precision lowp float;
 
 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;
 
 uniform sampler2D inputImageTexture;
 
 void main()
 {
     float bottomLeftIntensity = texture2D(inputImageTexture, bottomLeftTextureCoordinate).r;
     float topRightIntensity = texture2D(inputImageTexture, topRightTextureCoordinate).r;
     float topLeftIntensity = texture2D(inputImageTexture, topLeftTextureCoordinate).r;
     float bottomRightIntensity = texture2D(inputImageTexture, bottomRightTextureCoordinate).r;
     float leftIntensity = texture2D(inputImageTexture, leftTextureCoordinate).r;
     float rightIntensity = texture2D(inputImageTexture, rightTextureCoordinate).r;
     float bottomIntensity = texture2D(inputImageTexture, bottomTextureCoordinate).r;
     float topIntensity = texture2D(inputImageTexture, topTextureCoordinate).r;
     float centerIntensity = texture2D(inputImageTexture, textureCoordinate).r;
     
     float pixelIntensitySum = bottomLeftIntensity + topRightIntensity + topLeftIntensity + bottomRightIntensity + leftIntensity + rightIntensity + bottomIntensity + topIntensity + centerIntensity;
     float sumTest = step(1.5, pixelIntensitySum);
     float pixelTest = step(0.01, centerIntensity);
          
     gl_FragColor = vec4(vec3(sumTest * pixelTest), 1.0);
 }
);
#else
NSString *const kGPUImageWeakPixelInclusionFragmentShaderString = SHADER_STRING
(
 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;
 
 uniform sampler2D inputImageTexture;
 
 void main()
 {
     float bottomLeftIntensity = texture2D(inputImageTexture, bottomLeftTextureCoordinate).r;
     float topRightIntensity = texture2D(inputImageTexture, topRightTextureCoordinate).r;
     float topLeftIntensity = texture2D(inputImageTexture, topLeftTextureCoordinate).r;
     float bottomRightIntensity = texture2D(inputImageTexture, bottomRightTextureCoordinate).r;
     float leftIntensity = texture2D(inputImageTexture, leftTextureCoordinate).r;
     float rightIntensity = texture2D(inputImageTexture, rightTextureCoordinate).r;
     float bottomIntensity = texture2D(inputImageTexture, bottomTextureCoordinate).r;
     float topIntensity = texture2D(inputImageTexture, topTextureCoordinate).r;
     float centerIntensity = texture2D(inputImageTexture, textureCoordinate).r;
     
     float pixelIntensitySum = bottomLeftIntensity + topRightIntensity + topLeftIntensity + bottomRightIntensity + leftIntensity + rightIntensity + bottomIntensity + topIntensity + centerIntensity;
     float sumTest = step(1.5, pixelIntensitySum);
     float pixelTest = step(0.01, centerIntensity);
     
     gl_FragColor = vec4(vec3(sumTest * pixelTest), 1.0);
 }
);
#endif

#pragma mark -
#pragma mark Initialization and teardown

- (id)init;
{
    if (!(self = [self initWithFragmentShaderFromString:kGPUImageWeakPixelInclusionFragmentShaderString]))
    {
		return nil;
    }
    
    return self;
}

@end
