#import "GPUImageCrosshatchFilter.h"
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// Shader code based on http://machinesdontcare.wordpress.com/
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#if TARGET_IPHONE_SIMULATOR || TARGET_OS_IPHONE
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NSString *const kGPUImageCrosshatchFragmentShaderString = 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 highp float crossHatchSpacing;
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uniform highp float lineWidth;
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const highp vec3 W = vec3(0.2125, 0.7154, 0.0721);
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void main()
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{
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highp float luminance = dot(texture2D(inputImageTexture, textureCoordinate).rgb, W);
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lowp vec4 colorToDisplay = vec4(1.0, 1.0, 1.0, 1.0);
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if (luminance < 1.00)
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{
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if (mod(textureCoordinate.x + textureCoordinate.y, crossHatchSpacing) <= lineWidth)
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{
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colorToDisplay = vec4(0.0, 0.0, 0.0, 1.0);
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}
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}
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if (luminance < 0.75)
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{
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if (mod(textureCoordinate.x - textureCoordinate.y, crossHatchSpacing) <= lineWidth)
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{
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colorToDisplay = vec4(0.0, 0.0, 0.0, 1.0);
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}
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}
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if (luminance < 0.50)
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{
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if (mod(textureCoordinate.x + textureCoordinate.y - (crossHatchSpacing / 2.0), crossHatchSpacing) <= lineWidth)
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{
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colorToDisplay = vec4(0.0, 0.0, 0.0, 1.0);
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}
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}
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if (luminance < 0.3)
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{
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if (mod(textureCoordinate.x - textureCoordinate.y - (crossHatchSpacing / 2.0), crossHatchSpacing) <= lineWidth)
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{
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colorToDisplay = vec4(0.0, 0.0, 0.0, 1.0);
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}
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}
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gl_FragColor = colorToDisplay;
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}
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);
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#else
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NSString *const kGPUImageCrosshatchFragmentShaderString = 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 crossHatchSpacing;
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uniform float lineWidth;
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const vec3 W = vec3(0.2125, 0.7154, 0.0721);
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void main()
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{
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float luminance = dot(texture2D(inputImageTexture, textureCoordinate).rgb, W);
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vec4 colorToDisplay = vec4(1.0, 1.0, 1.0, 1.0);
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if (luminance < 1.00)
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{
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if (mod(textureCoordinate.x + textureCoordinate.y, crossHatchSpacing) <= lineWidth)
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{
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colorToDisplay = vec4(0.0, 0.0, 0.0, 1.0);
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}
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}
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if (luminance < 0.75)
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{
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if (mod(textureCoordinate.x - textureCoordinate.y, crossHatchSpacing) <= lineWidth)
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{
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colorToDisplay = vec4(0.0, 0.0, 0.0, 1.0);
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}
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}
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if (luminance < 0.50)
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{
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if (mod(textureCoordinate.x + textureCoordinate.y - (crossHatchSpacing / 2.0), crossHatchSpacing) <= lineWidth)
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{
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colorToDisplay = vec4(0.0, 0.0, 0.0, 1.0);
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}
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}
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if (luminance < 0.3)
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{
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if (mod(textureCoordinate.x - textureCoordinate.y - (crossHatchSpacing / 2.0), crossHatchSpacing) <= lineWidth)
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{
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colorToDisplay = vec4(0.0, 0.0, 0.0, 1.0);
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}
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}
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gl_FragColor = colorToDisplay;
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}
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);
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#endif
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@implementation GPUImageCrosshatchFilter
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@synthesize crossHatchSpacing = _crossHatchSpacing;
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@synthesize lineWidth = _lineWidth;
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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:kGPUImageCrosshatchFragmentShaderString]))
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{
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return nil;
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}
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crossHatchSpacingUniform = [filterProgram uniformIndex:@"crossHatchSpacing"];
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lineWidthUniform = [filterProgram uniformIndex:@"lineWidth"];
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self.crossHatchSpacing = 0.03;
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self.lineWidth = 0.003;
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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)setCrossHatchSpacing:(CGFloat)newValue;
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{
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CGFloat singlePixelSpacing;
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if (inputTextureSize.width != 0.0)
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{
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singlePixelSpacing = 1.0 / inputTextureSize.width;
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}
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else
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{
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singlePixelSpacing = 1.0 / 2048.0;
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}
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if (newValue < singlePixelSpacing)
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{
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_crossHatchSpacing = singlePixelSpacing;
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}
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else
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{
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_crossHatchSpacing = newValue;
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}
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[self setFloat:_crossHatchSpacing forUniform:crossHatchSpacingUniform program:filterProgram];
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}
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- (void)setLineWidth:(CGFloat)newValue;
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{
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_lineWidth = newValue;
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[self setFloat:_lineWidth forUniform:lineWidthUniform program:filterProgram];
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}
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@end
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