#import "GPUImageSaturationFilter.h"
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#if TARGET_IPHONE_SIMULATOR || TARGET_OS_IPHONE
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NSString *const kGPUImageSaturationFragmentShaderString = SHADER_STRING
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(
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varying highp vec2 textureCoordinate;
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uniform sampler2D inputImageTexture;
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uniform lowp float saturation;
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// Values from "Graphics Shaders: Theory and Practice" by Bailey and Cunningham
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const mediump vec3 luminanceWeighting = vec3(0.2125, 0.7154, 0.0721);
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void main()
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{
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lowp vec4 textureColor = texture2D(inputImageTexture, textureCoordinate);
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lowp float luminance = dot(textureColor.rgb, luminanceWeighting);
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lowp vec3 greyScaleColor = vec3(luminance);
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gl_FragColor = vec4(mix(greyScaleColor, textureColor.rgb, saturation), textureColor.w);
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}
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);
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#else
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NSString *const kGPUImageSaturationFragmentShaderString = SHADER_STRING
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(
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varying vec2 textureCoordinate;
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uniform sampler2D inputImageTexture;
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uniform float saturation;
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// Values from "Graphics Shaders: Theory and Practice" by Bailey and Cunningham
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const vec3 luminanceWeighting = vec3(0.2125, 0.7154, 0.0721);
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void main()
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{
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vec4 textureColor = texture2D(inputImageTexture, textureCoordinate);
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float luminance = dot(textureColor.rgb, luminanceWeighting);
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vec3 greyScaleColor = vec3(luminance);
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gl_FragColor = vec4(mix(greyScaleColor, textureColor.rgb, saturation), textureColor.w);
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}
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);
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#endif
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@implementation GPUImageSaturationFilter
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@synthesize saturation = _saturation;
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#pragma mark -
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#pragma mark Initialization and teardown
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- (id)init;
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{
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if (!(self = [super initWithFragmentShaderFromString:kGPUImageSaturationFragmentShaderString]))
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{
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return nil;
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}
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saturationUniform = [filterProgram uniformIndex:@"saturation"];
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self.saturation = 1.0;
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return self;
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}
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#pragma mark -
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#pragma mark Accessors
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- (void)setSaturation:(CGFloat)newValue;
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{
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_saturation = newValue;
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[self setFloat:_saturation forUniform:saturationUniform program:filterProgram];
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}
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@end
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