framework/Source/GPUImageSolarizeFilter.m
#import "GPUImageSolarizeFilter.h"

#if TARGET_IPHONE_SIMULATOR || TARGET_OS_IPHONE
NSString *const kGPUImageSolarizeFragmentShaderString = SHADER_STRING
(
 varying highp vec2 textureCoordinate;
 
 uniform sampler2D inputImageTexture;
 uniform highp float threshold;
 
 const highp vec3 W = vec3(0.2125, 0.7154, 0.0721);
 
 void main()
 {
     highp vec4 textureColor = texture2D(inputImageTexture, textureCoordinate);
     highp float luminance = dot(textureColor.rgb, W);
     highp float thresholdResult = step(luminance, threshold);
     highp vec3 finalColor = abs(thresholdResult - textureColor.rgb);
     
     gl_FragColor = vec4(finalColor, textureColor.w);
 }
);
#else
NSString *const kGPUImageSolarizeFragmentShaderString = SHADER_STRING
(
 varying vec2 textureCoordinate;
 
 uniform sampler2D inputImageTexture;
 uniform float threshold;
 
 const vec3 W = vec3(0.2125, 0.7154, 0.0721);
 
 void main()
 {
     vec4 textureColor = texture2D(inputImageTexture, textureCoordinate);
     float luminance = dot(textureColor.rgb, W);
     float thresholdResult = step(luminance, threshold);
     vec3 finalColor = abs(thresholdResult - textureColor.rgb);

     gl_FragColor = vec4(vec3(finalColor), textureColor.w);
 }
);
#endif

@implementation GPUImageSolarizeFilter;

@synthesize threshold = _threshold;

#pragma mark -
#pragma mark Initialization

- (id)init;
{
    if (!(self = [super initWithFragmentShaderFromString:kGPUImageSolarizeFragmentShaderString]))
    {
        return nil;
    }
    
    thresholdUniform = [filterProgram uniformIndex:@"threshold"];
    self.threshold = 0.5;
    
    return self;
}

#pragma mark -
#pragma mark Accessors

- (void)setThreshold:(CGFloat)newValue;
{
    _threshold = newValue;
    
    [self setFloat:_threshold forUniform:thresholdUniform program:filterProgram];
}


@end