developer
2023-05-20 e12c7b4c22df631ebdcd16b2f98fbef8f738f92f
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#import "GPUImagePolkaDotFilter.h"
 
#if TARGET_IPHONE_SIMULATOR || TARGET_OS_IPHONE
NSString *const kGPUImagePolkaDotFragmentShaderString = SHADER_STRING
(
 varying highp vec2 textureCoordinate;
 
 uniform sampler2D inputImageTexture;
 
 uniform highp float fractionalWidthOfPixel;
 uniform highp float aspectRatio;
 uniform highp float dotScaling;
 
 void main()
 {
     highp vec2 sampleDivisor = vec2(fractionalWidthOfPixel, fractionalWidthOfPixel / aspectRatio);
     
     highp vec2 samplePos = textureCoordinate - mod(textureCoordinate, sampleDivisor) + 0.5 * sampleDivisor;
     highp vec2 textureCoordinateToUse = vec2(textureCoordinate.x, (textureCoordinate.y * aspectRatio + 0.5 - 0.5 * aspectRatio));
     highp vec2 adjustedSamplePos = vec2(samplePos.x, (samplePos.y * aspectRatio + 0.5 - 0.5 * aspectRatio));
     highp float distanceFromSamplePoint = distance(adjustedSamplePos, textureCoordinateToUse);
     lowp float checkForPresenceWithinDot = step(distanceFromSamplePoint, (fractionalWidthOfPixel * 0.5) * dotScaling);
 
     lowp vec4 inputColor = texture2D(inputImageTexture, samplePos);
     
     gl_FragColor = vec4(inputColor.rgb * checkForPresenceWithinDot, inputColor.a);
 }
);
#else
NSString *const kGPUImagePolkaDotFragmentShaderString = SHADER_STRING
(
 varying vec2 textureCoordinate;
 
 uniform sampler2D inputImageTexture;
 
 uniform float fractionalWidthOfPixel;
 uniform float aspectRatio;
 uniform float dotScaling;
 
 void main()
 {
     vec2 sampleDivisor = vec2(fractionalWidthOfPixel, fractionalWidthOfPixel / aspectRatio);
     
     vec2 samplePos = textureCoordinate - mod(textureCoordinate, sampleDivisor) + 0.5 * sampleDivisor;
     vec2 textureCoordinateToUse = vec2(textureCoordinate.x, (textureCoordinate.y * aspectRatio + 0.5 - 0.5 * aspectRatio));
     vec2 adjustedSamplePos = vec2(samplePos.x, (samplePos.y * aspectRatio + 0.5 - 0.5 * aspectRatio));
     float distanceFromSamplePoint = distance(adjustedSamplePos, textureCoordinateToUse);
     float checkForPresenceWithinDot = step(distanceFromSamplePoint, (fractionalWidthOfPixel * 0.5) * dotScaling);
     
     vec4 inputColor = texture2D(inputImageTexture, samplePos);
 
     gl_FragColor = vec4(inputColor.rgb * checkForPresenceWithinDot, inputColor.a);
 }
);
#endif
 
@implementation GPUImagePolkaDotFilter
 
@synthesize dotScaling = _dotScaling;
 
- (id)init;
{
    if (!(self = [super initWithFragmentShaderFromString:kGPUImagePolkaDotFragmentShaderString]))
    {
        return nil;
    }
    
    dotScalingUniform = [filterProgram uniformIndex:@"dotScaling"];
    
    self.dotScaling = 0.90;
 
    return self;
}
 
#pragma mark -
#pragma mark Accessors
 
- (void)setDotScaling:(CGFloat)newValue;
{
    _dotScaling = newValue;
    
    [self setFloat:_dotScaling forUniform:dotScalingUniform program:filterProgram];
}
 
@end