#import "GPUImageLanczosResamplingFilter.h"
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NSString *const kGPUImageLanczosVertexShaderString = SHADER_STRING
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(
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attribute vec4 position;
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attribute vec2 inputTextureCoordinate;
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uniform float texelWidthOffset;
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uniform float texelHeightOffset;
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varying vec2 centerTextureCoordinate;
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varying vec2 oneStepLeftTextureCoordinate;
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varying vec2 twoStepsLeftTextureCoordinate;
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varying vec2 threeStepsLeftTextureCoordinate;
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varying vec2 fourStepsLeftTextureCoordinate;
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varying vec2 oneStepRightTextureCoordinate;
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varying vec2 twoStepsRightTextureCoordinate;
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varying vec2 threeStepsRightTextureCoordinate;
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varying vec2 fourStepsRightTextureCoordinate;
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void main()
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{
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gl_Position = position;
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vec2 firstOffset = vec2(texelWidthOffset, texelHeightOffset);
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vec2 secondOffset = vec2(2.0 * texelWidthOffset, 2.0 * texelHeightOffset);
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vec2 thirdOffset = vec2(3.0 * texelWidthOffset, 3.0 * texelHeightOffset);
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vec2 fourthOffset = vec2(4.0 * texelWidthOffset, 4.0 * texelHeightOffset);
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centerTextureCoordinate = inputTextureCoordinate;
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oneStepLeftTextureCoordinate = inputTextureCoordinate - firstOffset;
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twoStepsLeftTextureCoordinate = inputTextureCoordinate - secondOffset;
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threeStepsLeftTextureCoordinate = inputTextureCoordinate - thirdOffset;
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fourStepsLeftTextureCoordinate = inputTextureCoordinate - fourthOffset;
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oneStepRightTextureCoordinate = inputTextureCoordinate + firstOffset;
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twoStepsRightTextureCoordinate = inputTextureCoordinate + secondOffset;
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threeStepsRightTextureCoordinate = inputTextureCoordinate + thirdOffset;
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fourStepsRightTextureCoordinate = inputTextureCoordinate + fourthOffset;
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}
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);
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#if TARGET_IPHONE_SIMULATOR || TARGET_OS_IPHONE
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NSString *const kGPUImageLanczosFragmentShaderString = SHADER_STRING
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(
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precision highp float;
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uniform sampler2D inputImageTexture;
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varying vec2 centerTextureCoordinate;
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varying vec2 oneStepLeftTextureCoordinate;
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varying vec2 twoStepsLeftTextureCoordinate;
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varying vec2 threeStepsLeftTextureCoordinate;
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varying vec2 fourStepsLeftTextureCoordinate;
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varying vec2 oneStepRightTextureCoordinate;
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varying vec2 twoStepsRightTextureCoordinate;
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varying vec2 threeStepsRightTextureCoordinate;
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varying vec2 fourStepsRightTextureCoordinate;
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// sinc(x) * sinc(x/a) = (a * sin(pi * x) * sin(pi * x / a)) / (pi^2 * x^2)
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// Assuming a Lanczos constant of 2.0, and scaling values to max out at x = +/- 1.5
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void main()
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{
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lowp vec4 fragmentColor = texture2D(inputImageTexture, centerTextureCoordinate) * 0.38026;
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fragmentColor += texture2D(inputImageTexture, oneStepLeftTextureCoordinate) * 0.27667;
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fragmentColor += texture2D(inputImageTexture, oneStepRightTextureCoordinate) * 0.27667;
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fragmentColor += texture2D(inputImageTexture, twoStepsLeftTextureCoordinate) * 0.08074;
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fragmentColor += texture2D(inputImageTexture, twoStepsRightTextureCoordinate) * 0.08074;
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fragmentColor += texture2D(inputImageTexture, threeStepsLeftTextureCoordinate) * -0.02612;
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fragmentColor += texture2D(inputImageTexture, threeStepsRightTextureCoordinate) * -0.02612;
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fragmentColor += texture2D(inputImageTexture, fourStepsLeftTextureCoordinate) * -0.02143;
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fragmentColor += texture2D(inputImageTexture, fourStepsRightTextureCoordinate) * -0.02143;
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gl_FragColor = fragmentColor;
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}
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);
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#else
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NSString *const kGPUImageLanczosFragmentShaderString = SHADER_STRING
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(
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uniform sampler2D inputImageTexture;
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varying vec2 centerTextureCoordinate;
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varying vec2 oneStepLeftTextureCoordinate;
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varying vec2 twoStepsLeftTextureCoordinate;
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varying vec2 threeStepsLeftTextureCoordinate;
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varying vec2 fourStepsLeftTextureCoordinate;
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varying vec2 oneStepRightTextureCoordinate;
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varying vec2 twoStepsRightTextureCoordinate;
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varying vec2 threeStepsRightTextureCoordinate;
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varying vec2 fourStepsRightTextureCoordinate;
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// sinc(x) * sinc(x/a) = (a * sin(pi * x) * sin(pi * x / a)) / (pi^2 * x^2)
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// Assuming a Lanczos constant of 2.0, and scaling values to max out at x = +/- 1.5
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void main()
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{
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vec4 fragmentColor = texture2D(inputImageTexture, centerTextureCoordinate) * 0.38026;
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fragmentColor += texture2D(inputImageTexture, oneStepLeftTextureCoordinate) * 0.27667;
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fragmentColor += texture2D(inputImageTexture, oneStepRightTextureCoordinate) * 0.27667;
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fragmentColor += texture2D(inputImageTexture, twoStepsLeftTextureCoordinate) * 0.08074;
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fragmentColor += texture2D(inputImageTexture, twoStepsRightTextureCoordinate) * 0.08074;
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fragmentColor += texture2D(inputImageTexture, threeStepsLeftTextureCoordinate) * -0.02612;
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fragmentColor += texture2D(inputImageTexture, threeStepsRightTextureCoordinate) * -0.02612;
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fragmentColor += texture2D(inputImageTexture, fourStepsLeftTextureCoordinate) * -0.02143;
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fragmentColor += texture2D(inputImageTexture, fourStepsRightTextureCoordinate) * -0.02143;
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gl_FragColor = fragmentColor;
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}
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);
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#endif
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@implementation GPUImageLanczosResamplingFilter
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@synthesize originalImageSize = _originalImageSize;
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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 initWithFirstStageVertexShaderFromString:kGPUImageLanczosVertexShaderString firstStageFragmentShaderFromString:kGPUImageLanczosFragmentShaderString secondStageVertexShaderFromString:kGPUImageLanczosVertexShaderString secondStageFragmentShaderFromString:kGPUImageLanczosFragmentShaderString]))
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{
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return nil;
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}
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return self;
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}
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// Base texture sampling offset on the input image, not the final size
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- (void)setInputSize:(CGSize)newSize atIndex:(NSInteger)textureIndex;
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{
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self.originalImageSize = newSize;
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[super setInputSize:newSize atIndex:textureIndex];
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}
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- (void)setupFilterForSize:(CGSize)filterFrameSize;
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{
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runSynchronouslyOnVideoProcessingQueue(^{
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// The first pass through the framebuffer may rotate the inbound image, so need to account for that by changing up the kernel ordering for that pass
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if (GPUImageRotationSwapsWidthAndHeight(inputRotation))
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{
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verticalPassTexelWidthOffset = 1.0 / _originalImageSize.height;
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verticalPassTexelHeightOffset = 0.0;
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}
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else
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{
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verticalPassTexelWidthOffset = 0.0;
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verticalPassTexelHeightOffset = 1.0 / _originalImageSize.height;
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}
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horizontalPassTexelWidthOffset = 1.0 / _originalImageSize.width;
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horizontalPassTexelHeightOffset = 0.0;
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});
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}
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- (void)renderToTextureWithVertices:(const GLfloat *)vertices textureCoordinates:(const GLfloat *)textureCoordinates;
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{
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if (self.preventRendering)
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{
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[firstInputFramebuffer unlock];
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return;
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}
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[GPUImageContext setActiveShaderProgram:filterProgram];
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CGSize currentFBOSize = [self sizeOfFBO];
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if (GPUImageRotationSwapsWidthAndHeight(inputRotation))
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{
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currentFBOSize.height = self.originalImageSize.height;
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}
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else
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{
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currentFBOSize.width = self.originalImageSize.width;
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}
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outputFramebuffer = [[GPUImageContext sharedFramebufferCache] fetchFramebufferForSize:currentFBOSize textureOptions:self.outputTextureOptions onlyTexture:NO];
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[outputFramebuffer activateFramebuffer];
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[self setUniformsForProgramAtIndex:0];
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glClearColor(backgroundColorRed, backgroundColorGreen, backgroundColorBlue, backgroundColorAlpha);
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glClear(GL_COLOR_BUFFER_BIT);
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glActiveTexture(GL_TEXTURE2);
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glBindTexture(GL_TEXTURE_2D, [firstInputFramebuffer texture]);
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glUniform1i(filterInputTextureUniform, 2);
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glVertexAttribPointer(filterPositionAttribute, 2, GL_FLOAT, 0, 0, vertices);
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glVertexAttribPointer(filterTextureCoordinateAttribute, 2, GL_FLOAT, 0, 0, textureCoordinates);
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glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
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[firstInputFramebuffer unlock];
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// Run the second stage of the two-pass filter
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[GPUImageContext setActiveShaderProgram:secondFilterProgram];
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glActiveTexture(GL_TEXTURE2);
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glBindTexture(GL_TEXTURE_2D, 0);
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glActiveTexture(GL_TEXTURE3);
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glBindTexture(GL_TEXTURE_2D, 0);
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secondOutputFramebuffer = [[GPUImageContext sharedFramebufferCache] fetchFramebufferForSize:[self sizeOfFBO] textureOptions:self.outputTextureOptions onlyTexture:NO];
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[secondOutputFramebuffer activateFramebuffer];
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if (usingNextFrameForImageCapture)
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{
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[secondOutputFramebuffer lock];
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}
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[self setUniformsForProgramAtIndex:1];
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glActiveTexture(GL_TEXTURE3);
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glBindTexture(GL_TEXTURE_2D, [outputFramebuffer texture]);
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glVertexAttribPointer(secondFilterTextureCoordinateAttribute, 2, GL_FLOAT, 0, 0, [[self class] textureCoordinatesForRotation:kGPUImageNoRotation]);
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glUniform1i(secondFilterInputTextureUniform, 3);
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glVertexAttribPointer(secondFilterPositionAttribute, 2, GL_FLOAT, 0, 0, vertices);
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glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
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glClear(GL_COLOR_BUFFER_BIT);
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glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
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[outputFramebuffer unlock];
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outputFramebuffer = nil;
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if (usingNextFrameForImageCapture)
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{
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dispatch_semaphore_signal(imageCaptureSemaphore);
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}
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}
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@end
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