#import "GPUImageMedianFilter.h"
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/*
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3x3 median filter, adapted from "A Fast, Small-Radius GPU Median Filter" by Morgan McGuire in ShaderX6
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http://graphics.cs.williams.edu/papers/MedianShaderX6/
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Morgan McGuire and Kyle Whitson
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Williams College
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Register allocation tips by Victor Huang Xiaohuang
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University of Illinois at Urbana-Champaign
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http://graphics.cs.williams.edu
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Copyright (c) Morgan McGuire and Williams College, 2006
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All rights reserved.
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions are
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met:
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Redistributions of source code must retain the above copyright notice,
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this list of conditions and the following disclaimer.
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Redistributions in binary form must reproduce the above copyright
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notice, this list of conditions and the following disclaimer in the
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documentation and/or other materials provided with the distribution.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#if TARGET_IPHONE_SIMULATOR || TARGET_OS_IPHONE
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NSString *const kGPUImageMedianFragmentShaderString = SHADER_STRING
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(
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precision highp float;
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varying vec2 textureCoordinate;
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varying vec2 leftTextureCoordinate;
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varying vec2 rightTextureCoordinate;
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varying vec2 topTextureCoordinate;
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varying vec2 topLeftTextureCoordinate;
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varying vec2 topRightTextureCoordinate;
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varying vec2 bottomTextureCoordinate;
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varying vec2 bottomLeftTextureCoordinate;
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varying vec2 bottomRightTextureCoordinate;
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uniform sampler2D inputImageTexture;
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#define s2(a, b) temp = a; a = min(a, b); b = max(temp, b);
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#define mn3(a, b, c) s2(a, b); s2(a, c);
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#define mx3(a, b, c) s2(b, c); s2(a, c);
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#define mnmx3(a, b, c) mx3(a, b, c); s2(a, b); // 3 exchanges
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#define mnmx4(a, b, c, d) s2(a, b); s2(c, d); s2(a, c); s2(b, d); // 4 exchanges
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#define mnmx5(a, b, c, d, e) s2(a, b); s2(c, d); mn3(a, c, e); mx3(b, d, e); // 6 exchanges
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#define mnmx6(a, b, c, d, e, f) s2(a, d); s2(b, e); s2(c, f); mn3(a, b, c); mx3(d, e, f); // 7 exchanges
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void main()
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{
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vec3 v[6];
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v[0] = texture2D(inputImageTexture, bottomLeftTextureCoordinate).rgb;
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v[1] = texture2D(inputImageTexture, topRightTextureCoordinate).rgb;
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v[2] = texture2D(inputImageTexture, topLeftTextureCoordinate).rgb;
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v[3] = texture2D(inputImageTexture, bottomRightTextureCoordinate).rgb;
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v[4] = texture2D(inputImageTexture, leftTextureCoordinate).rgb;
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v[5] = texture2D(inputImageTexture, rightTextureCoordinate).rgb;
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// v[6] = texture2D(inputImageTexture, bottomTextureCoordinate).rgb;
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// v[7] = texture2D(inputImageTexture, topTextureCoordinate).rgb;
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vec3 temp;
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mnmx6(v[0], v[1], v[2], v[3], v[4], v[5]);
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v[5] = texture2D(inputImageTexture, bottomTextureCoordinate).rgb;
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mnmx5(v[1], v[2], v[3], v[4], v[5]);
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v[5] = texture2D(inputImageTexture, topTextureCoordinate).rgb;
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mnmx4(v[2], v[3], v[4], v[5]);
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v[5] = texture2D(inputImageTexture, textureCoordinate).rgb;
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mnmx3(v[3], v[4], v[5]);
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gl_FragColor = vec4(v[4], 1.0);
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}
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);
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#else
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NSString *const kGPUImageMedianFragmentShaderString = SHADER_STRING
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(
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varying vec2 textureCoordinate;
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varying vec2 leftTextureCoordinate;
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varying vec2 rightTextureCoordinate;
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varying vec2 topTextureCoordinate;
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varying vec2 topLeftTextureCoordinate;
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varying vec2 topRightTextureCoordinate;
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varying vec2 bottomTextureCoordinate;
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varying vec2 bottomLeftTextureCoordinate;
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varying vec2 bottomRightTextureCoordinate;
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uniform sampler2D inputImageTexture;
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#define s2(a, b) temp = a; a = min(a, b); b = max(temp, b);
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#define mn3(a, b, c) s2(a, b); s2(a, c);
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#define mx3(a, b, c) s2(b, c); s2(a, c);
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#define mnmx3(a, b, c) mx3(a, b, c); s2(a, b); // 3 exchanges
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#define mnmx4(a, b, c, d) s2(a, b); s2(c, d); s2(a, c); s2(b, d); // 4 exchanges
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#define mnmx5(a, b, c, d, e) s2(a, b); s2(c, d); mn3(a, c, e); mx3(b, d, e); // 6 exchanges
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#define mnmx6(a, b, c, d, e, f) s2(a, d); s2(b, e); s2(c, f); mn3(a, b, c); mx3(d, e, f); // 7 exchanges
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void main()
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{
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vec3 v[6];
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v[0] = texture2D(inputImageTexture, bottomLeftTextureCoordinate).rgb;
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v[1] = texture2D(inputImageTexture, topRightTextureCoordinate).rgb;
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v[2] = texture2D(inputImageTexture, topLeftTextureCoordinate).rgb;
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v[3] = texture2D(inputImageTexture, bottomRightTextureCoordinate).rgb;
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v[4] = texture2D(inputImageTexture, leftTextureCoordinate).rgb;
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v[5] = texture2D(inputImageTexture, rightTextureCoordinate).rgb;
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// v[6] = texture2D(inputImageTexture, bottomTextureCoordinate).rgb;
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// v[7] = texture2D(inputImageTexture, topTextureCoordinate).rgb;
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vec3 temp;
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mnmx6(v[0], v[1], v[2], v[3], v[4], v[5]);
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v[5] = texture2D(inputImageTexture, bottomTextureCoordinate).rgb;
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mnmx5(v[1], v[2], v[3], v[4], v[5]);
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v[5] = texture2D(inputImageTexture, topTextureCoordinate).rgb;
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mnmx4(v[2], v[3], v[4], v[5]);
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v[5] = texture2D(inputImageTexture, textureCoordinate).rgb;
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mnmx3(v[3], v[4], v[5]);
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gl_FragColor = vec4(v[4], 1.0);
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}
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);
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#endif
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@implementation GPUImageMedianFilter
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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:kGPUImageMedianFragmentShaderString]))
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{
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return nil;
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}
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hasOverriddenImageSizeFactor = NO;
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return self;
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}
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@end
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