#import "GPUImageSobelEdgeDetectionFilter.h"
|
#import "GPUImageGrayscaleFilter.h"
|
#import "GPUImage3x3ConvolutionFilter.h"
|
|
// Code from "Graphics Shaders: Theory and Practice" by M. Bailey and S. Cunningham
|
#if TARGET_IPHONE_SIMULATOR || TARGET_OS_IPHONE
|
NSString *const kGPUImageSobelEdgeDetectionFragmentShaderString = SHADER_STRING
|
(
|
precision mediump float;
|
|
varying vec2 textureCoordinate;
|
varying vec2 leftTextureCoordinate;
|
varying vec2 rightTextureCoordinate;
|
|
varying vec2 topTextureCoordinate;
|
varying vec2 topLeftTextureCoordinate;
|
varying vec2 topRightTextureCoordinate;
|
|
varying vec2 bottomTextureCoordinate;
|
varying vec2 bottomLeftTextureCoordinate;
|
varying vec2 bottomRightTextureCoordinate;
|
|
uniform sampler2D inputImageTexture;
|
uniform float edgeStrength;
|
|
void main()
|
{
|
float bottomLeftIntensity = texture2D(inputImageTexture, bottomLeftTextureCoordinate).r;
|
float topRightIntensity = texture2D(inputImageTexture, topRightTextureCoordinate).r;
|
float topLeftIntensity = texture2D(inputImageTexture, topLeftTextureCoordinate).r;
|
float bottomRightIntensity = texture2D(inputImageTexture, bottomRightTextureCoordinate).r;
|
float leftIntensity = texture2D(inputImageTexture, leftTextureCoordinate).r;
|
float rightIntensity = texture2D(inputImageTexture, rightTextureCoordinate).r;
|
float bottomIntensity = texture2D(inputImageTexture, bottomTextureCoordinate).r;
|
float topIntensity = texture2D(inputImageTexture, topTextureCoordinate).r;
|
float h = -topLeftIntensity - 2.0 * topIntensity - topRightIntensity + bottomLeftIntensity + 2.0 * bottomIntensity + bottomRightIntensity;
|
float v = -bottomLeftIntensity - 2.0 * leftIntensity - topLeftIntensity + bottomRightIntensity + 2.0 * rightIntensity + topRightIntensity;
|
|
float mag = length(vec2(h, v)) * edgeStrength;
|
|
gl_FragColor = vec4(vec3(mag), 1.0);
|
}
|
);
|
#else
|
NSString *const kGPUImageSobelEdgeDetectionFragmentShaderString = SHADER_STRING
|
(
|
varying vec2 textureCoordinate;
|
varying vec2 leftTextureCoordinate;
|
varying vec2 rightTextureCoordinate;
|
|
varying vec2 topTextureCoordinate;
|
varying vec2 topLeftTextureCoordinate;
|
varying vec2 topRightTextureCoordinate;
|
|
varying vec2 bottomTextureCoordinate;
|
varying vec2 bottomLeftTextureCoordinate;
|
varying vec2 bottomRightTextureCoordinate;
|
|
uniform sampler2D inputImageTexture;
|
uniform float edgeStrength;
|
|
void main()
|
{
|
float bottomLeftIntensity = texture2D(inputImageTexture, bottomLeftTextureCoordinate).r;
|
float topRightIntensity = texture2D(inputImageTexture, topRightTextureCoordinate).r;
|
float topLeftIntensity = texture2D(inputImageTexture, topLeftTextureCoordinate).r;
|
float bottomRightIntensity = texture2D(inputImageTexture, bottomRightTextureCoordinate).r;
|
float leftIntensity = texture2D(inputImageTexture, leftTextureCoordinate).r;
|
float rightIntensity = texture2D(inputImageTexture, rightTextureCoordinate).r;
|
float bottomIntensity = texture2D(inputImageTexture, bottomTextureCoordinate).r;
|
float topIntensity = texture2D(inputImageTexture, topTextureCoordinate).r;
|
float h = -topLeftIntensity - 2.0 * topIntensity - topRightIntensity + bottomLeftIntensity + 2.0 * bottomIntensity + bottomRightIntensity;
|
float v = -bottomLeftIntensity - 2.0 * leftIntensity - topLeftIntensity + bottomRightIntensity + 2.0 * rightIntensity + topRightIntensity;
|
|
float mag = length(vec2(h, v)) * edgeStrength;
|
|
gl_FragColor = vec4(vec3(mag), 1.0);
|
}
|
);
|
#endif
|
|
@implementation GPUImageSobelEdgeDetectionFilter
|
|
@synthesize texelWidth = _texelWidth;
|
@synthesize texelHeight = _texelHeight;
|
@synthesize edgeStrength = _edgeStrength;
|
|
#pragma mark -
|
#pragma mark Initialization and teardown
|
|
- (id)init;
|
{
|
if (!(self = [self initWithFragmentShaderFromString:kGPUImageSobelEdgeDetectionFragmentShaderString]))
|
{
|
return nil;
|
}
|
|
return self;
|
}
|
|
- (id)initWithFragmentShaderFromString:(NSString *)fragmentShaderString;
|
{
|
// Do a luminance pass first to reduce the calculations performed at each fragment in the edge detection phase
|
|
if (!(self = [super initWithFirstStageVertexShaderFromString:kGPUImageVertexShaderString firstStageFragmentShaderFromString:kGPUImageLuminanceFragmentShaderString secondStageVertexShaderFromString:kGPUImageNearbyTexelSamplingVertexShaderString secondStageFragmentShaderFromString:fragmentShaderString]))
|
{
|
return nil;
|
}
|
|
hasOverriddenImageSizeFactor = NO;
|
|
texelWidthUniform = [secondFilterProgram uniformIndex:@"texelWidth"];
|
texelHeightUniform = [secondFilterProgram uniformIndex:@"texelHeight"];
|
edgeStrengthUniform = [secondFilterProgram uniformIndex:@"edgeStrength"];
|
|
self.edgeStrength = 1.0;
|
return self;
|
}
|
|
- (void)setupFilterForSize:(CGSize)filterFrameSize;
|
{
|
if (!hasOverriddenImageSizeFactor)
|
{
|
_texelWidth = 1.0 / filterFrameSize.width;
|
_texelHeight = 1.0 / filterFrameSize.height;
|
|
runSynchronouslyOnVideoProcessingQueue(^{
|
GLProgram *previousProgram = [GPUImageContext sharedImageProcessingContext].currentShaderProgram;
|
[GPUImageContext setActiveShaderProgram:secondFilterProgram];
|
glUniform1f(texelWidthUniform, _texelWidth);
|
glUniform1f(texelHeightUniform, _texelHeight);
|
[GPUImageContext setActiveShaderProgram:previousProgram];
|
});
|
}
|
}
|
|
- (void)setUniformsForProgramAtIndex:(NSUInteger)programIndex;
|
{
|
[super setUniformsForProgramAtIndex:programIndex];
|
|
if (programIndex == 1)
|
{
|
glUniform1f(texelWidthUniform, _texelWidth);
|
glUniform1f(texelHeightUniform, _texelHeight);
|
}
|
}
|
|
- (BOOL)wantsMonochromeInput;
|
{
|
// return YES;
|
return NO;
|
}
|
|
- (BOOL)providesMonochromeOutput;
|
{
|
// return YES;
|
return NO;
|
}
|
|
#pragma mark -
|
#pragma mark Accessors
|
|
- (void)setTexelWidth:(CGFloat)newValue;
|
{
|
hasOverriddenImageSizeFactor = YES;
|
_texelWidth = newValue;
|
|
[self setFloat:_texelWidth forUniform:texelWidthUniform program:secondFilterProgram];
|
}
|
|
- (void)setTexelHeight:(CGFloat)newValue;
|
{
|
hasOverriddenImageSizeFactor = YES;
|
_texelHeight = newValue;
|
|
[self setFloat:_texelHeight forUniform:texelHeightUniform program:secondFilterProgram];
|
}
|
|
- (void)setEdgeStrength:(CGFloat)newValue;
|
{
|
_edgeStrength = newValue;
|
|
[self setFloat:_edgeStrength forUniform:edgeStrengthUniform program:secondFilterProgram];
|
}
|
|
|
@end
|
