Added a halftone filter.

README.md

@@ -293,6 +293,9 @@ Documentation is generated from header comments using appledoc. To build the doc
   - *fractionalWidthOfAPixel*: How large the dots are, as a fraction of the width and height of the image (0.0 - 1.0, default 0.05)
   - *dotScaling*: What fraction of each grid space is taken up by a dot, from 0.0 to 1.0 with a default of 0.9.
 
+- **GPUImageHalftoneFilter**: Applies a halftone effect to an image, like news print
+  - *fractionalWidthOfAPixel*: How large the halftone dots are, as a fraction of the width and height of the image (0.0 - 1.0, default 0.05)
+
 - **GPUImageCrosshatchFilter**: This converts an image into a black-and-white crosshatch pattern
   - *crossHatchSpacing*: The fractional width of the image to use as the spacing for the crosshatch. The default is 0.03.
   - *lineWidth*: A relative width for the crosshatch lines. The default is 0.003.

examples/FilterShowcase/FilterShowcase/ShowcaseFilterListController.m

@@ -104,6 +104,7 @@ - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(N
 		case GPUIMAGE_PIXELLATE: cell.textLabel.text = @"Pixellate"; break;
 		case GPUIMAGE_POLARPIXELLATE: cell.textLabel.text = @"Polar pixellate"; break;
 		case GPUIMAGE_POLKADOT: cell.textLabel.text = @"Polka dot"; break;
+		case GPUIMAGE_HALFTONE: cell.textLabel.text = @"Halftone"; break;
 		case GPUIMAGE_CROSSHATCH: cell.textLabel.text = @"Crosshatch"; break;
 		case GPUIMAGE_SOBELEDGEDETECTION: cell.textLabel.text = @"Sobel edge detection"; break;
 		case GPUIMAGE_PREWITTEDGEDETECTION: cell.textLabel.text = @"Prewitt edge detection"; break;

examples/FilterShowcase/FilterShowcase/ShowcaseFilterViewController.h

@@ -36,6 +36,7 @@ typedef enum {
     GPUIMAGE_PIXELLATE,
     GPUIMAGE_POLARPIXELLATE,
     GPUIMAGE_POLKADOT,
+    GPUIMAGE_HALFTONE,
     GPUIMAGE_CROSSHATCH,
     GPUIMAGE_SOBELEDGEDETECTION,
     GPUIMAGE_PREWITTEDGEDETECTION,

examples/FilterShowcase/FilterShowcase/ShowcaseFilterViewController.m

@@ -111,6 +111,17 @@ - (void)setupFilter;
 
             filter = [[GPUImagePolkaDotFilter alloc] init];
         }; break;
+        case GPUIMAGE_HALFTONE:
+        {
+            self.title = @"Halftone";
+            self.filterSettingsSlider.hidden = NO;
+
+            [self.filterSettingsSlider setValue:0.01];
+            [self.filterSettingsSlider setMinimumValue:0.0];
+            [self.filterSettingsSlider setMaximumValue:0.05];
+
+            filter = [[GPUImageHalftoneFilter alloc] init];
+        }; break;
         case GPUIMAGE_CROSSHATCH:
         {
             self.title = @"Crosshatch";
@@ -1335,6 +1346,7 @@ - (IBAction)updateFilterFromSlider:(id)sender;
         case GPUIMAGE_PIXELLATE: [(GPUImagePixellateFilter *)filter setFractionalWidthOfAPixel:[(UISlider *)sender value]]; break;
         case GPUIMAGE_POLARPIXELLATE: [(GPUImagePolarPixellateFilter *)filter setPixelSize:CGSizeMake([(UISlider *)sender value], [(UISlider *)sender value])]; break;
         case GPUIMAGE_POLKADOT: [(GPUImagePolkaDotFilter *)filter setFractionalWidthOfAPixel:[(UISlider *)sender value]]; break;
+        case GPUIMAGE_HALFTONE: [(GPUImageHalftoneFilter *)filter setFractionalWidthOfAPixel:[(UISlider *)sender value]]; break;
         case GPUIMAGE_SATURATION: [(GPUImageSaturationFilter *)filter setSaturation:[(UISlider *)sender value]]; break;
         case GPUIMAGE_CONTRAST: [(GPUImageContrastFilter *)filter setContrast:[(UISlider *)sender value]]; break;
         case GPUIMAGE_BRIGHTNESS: [(GPUImageBrightnessFilter *)filter setBrightness:[(UISlider *)sender value]]; break;

framework/GPUImage.xcodeproj/project.pbxproj

@@ -86,6 +86,8 @@
 		BC27A3CC15654F5A004F2D45 /* GPUImagePerlinNoiseFilter.m in Sources */ = {isa = PBXBuildFile; fileRef = BC27A3CA15654F5A004F2D45 /* GPUImagePerlinNoiseFilter.m */; };
 		BC3AC8B015E6F6170065144E /* GPUImageAverageColor.h in Headers */ = {isa = PBXBuildFile; fileRef = BC3AC8AE15E6F6170065144E /* GPUImageAverageColor.h */; };
 		BC3AC8B115E6F6170065144E /* GPUImageAverageColor.m in Sources */ = {isa = PBXBuildFile; fileRef = BC3AC8AF15E6F6170065144E /* GPUImageAverageColor.m */; };
+		BC4D03CF160919AE00F64358 /* GPUImageHalftoneFilter.h in Headers */ = {isa = PBXBuildFile; fileRef = BC4D03CD160919AE00F64358 /* GPUImageHalftoneFilter.h */; };
+		BC4D03D0160919AE00F64358 /* GPUImageHalftoneFilter.m in Sources */ = {isa = PBXBuildFile; fileRef = BC4D03CE160919AE00F64358 /* GPUImageHalftoneFilter.m */; };
 		BC54D563151904FF003F4A41 /* GPUImageChromaKeyBlendFilter.h in Headers */ = {isa = PBXBuildFile; fileRef = BC54D561151904FF003F4A41 /* GPUImageChromaKeyBlendFilter.h */; };
 		BC54D564151904FF003F4A41 /* GPUImageChromaKeyBlendFilter.m in Sources */ = {isa = PBXBuildFile; fileRef = BC54D562151904FF003F4A41 /* GPUImageChromaKeyBlendFilter.m */; };
 		BC56D82A1579779700CC9C1E /* GPUImageUIElement.h in Headers */ = {isa = PBXBuildFile; fileRef = BC56D8281579779700CC9C1E /* GPUImageUIElement.h */; };
@@ -388,6 +390,8 @@
 		BC27A3CA15654F5A004F2D45 /* GPUImagePerlinNoiseFilter.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; name = GPUImagePerlinNoiseFilter.m; path = Source/GPUImagePerlinNoiseFilter.m; sourceTree = SOURCE_ROOT; };
 		BC3AC8AE15E6F6170065144E /* GPUImageAverageColor.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; name = GPUImageAverageColor.h; path = Source/GPUImageAverageColor.h; sourceTree = SOURCE_ROOT; };
 		BC3AC8AF15E6F6170065144E /* GPUImageAverageColor.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; name = GPUImageAverageColor.m; path = Source/GPUImageAverageColor.m; sourceTree = SOURCE_ROOT; };
+		BC4D03CD160919AE00F64358 /* GPUImageHalftoneFilter.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; name = GPUImageHalftoneFilter.h; path = Source/GPUImageHalftoneFilter.h; sourceTree = SOURCE_ROOT; };
+		BC4D03CE160919AE00F64358 /* GPUImageHalftoneFilter.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; name = GPUImageHalftoneFilter.m; path = Source/GPUImageHalftoneFilter.m; sourceTree = SOURCE_ROOT; };
 		BC54D561151904FF003F4A41 /* GPUImageChromaKeyBlendFilter.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; name = GPUImageChromaKeyBlendFilter.h; path = Source/GPUImageChromaKeyBlendFilter.h; sourceTree = SOURCE_ROOT; };
 		BC54D562151904FF003F4A41 /* GPUImageChromaKeyBlendFilter.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; name = GPUImageChromaKeyBlendFilter.m; path = Source/GPUImageChromaKeyBlendFilter.m; sourceTree = SOURCE_ROOT; };
 		BC56D8281579779700CC9C1E /* GPUImageUIElement.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; name = GPUImageUIElement.h; path = Source/GPUImageUIElement.h; sourceTree = SOURCE_ROOT; };
@@ -769,6 +773,8 @@
 				BCB5DE0C14E87F32000AF3C2 /* GPUImagePixellateFilter.m */,
 				BCF851B815CF29B3000EBC8B /* GPUImagePolkaDotFilter.h */,
 				BCF851B915CF29B3000EBC8B /* GPUImagePolkaDotFilter.m */,
+				BC4D03CD160919AE00F64358 /* GPUImageHalftoneFilter.h */,
+				BC4D03CE160919AE00F64358 /* GPUImageHalftoneFilter.m */,
 				BCABED8A15263CF20098A93E /* GPUImagePolarPixellateFilter.h */,
 				BCABED8B15263CF20098A93E /* GPUImagePolarPixellateFilter.m */,
 				BCC1E669152368130006EFA5 /* GPUImageCrosshatchFilter.h */,
@@ -1187,6 +1193,7 @@
 				BCB3B46A15F2FD1B00EDA3BE /* GPUImageHighPassFilter.h in Headers */,
 				BCB3B47915F3108700EDA3BE /* GPUImageMotionDetector.h in Headers */,
 				4308B1D715F7EED30014437A /* GPUImageNormalBlendFilter.h in Headers */,
+				BC4D03CF160919AE00F64358 /* GPUImageHalftoneFilter.h in Headers */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};
@@ -1438,6 +1445,7 @@
 				BCB3B46B15F2FD1B00EDA3BE /* GPUImageHighPassFilter.m in Sources */,
 				BCB3B47A15F3108700EDA3BE /* GPUImageMotionDetector.m in Sources */,
 				4308B1D815F7EED30014437A /* GPUImageNormalBlendFilter.m in Sources */,
+				BC4D03D0160919AE00F64358 /* GPUImageHalftoneFilter.m in Sources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};

framework/Source/GPUImage.h

@@ -128,4 +128,5 @@
 #import "GPUImageChromaKeyFilter.h"
 #import "GPUImageLowPassFilter.h"
 #import "GPUImageHighPassFilter.h"
-#import "GPUImageMotionDetector.h"
+#import "GPUImageMotionDetector.h"
+#import "GPUImageHalftoneFilter.h"

framework/Source/GPUImageHalftoneFilter.h

@@ -0,0 +1,5 @@
+#import "GPUImagePixellateFilter.h"
+
+@interface GPUImageHalftoneFilter : GPUImagePixellateFilter
+
+@end

framework/Source/GPUImageHalftoneFilter.m

@@ -0,0 +1,47 @@
+#import "GPUImageHalftoneFilter.h"
+
+NSString *const kGPUImageHalftoneFragmentShaderString = SHADER_STRING
+(
+ varying highp vec2 textureCoordinate;
+
+ uniform sampler2D inputImageTexture;
+
+ uniform highp float fractionalWidthOfPixel;
+ uniform highp float aspectRatio;
+ uniform highp float dotScaling;
+
+ const highp vec3 W = vec3(0.2125, 0.7154, 0.0721);
+
+ 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 vec3 sampledColor = texture2D(inputImageTexture, samplePos ).rgb;
+     highp float dotScaling = 1.0 - dot(sampledColor, W);
+
+     lowp float checkForPresenceWithinDot = 1.0 - step(distanceFromSamplePoint, (fractionalWidthOfPixel * 0.5) * dotScaling);
+
+     gl_FragColor = vec4(vec3(checkForPresenceWithinDot), 1.0);
+ }
+ );
+
+@implementation GPUImageHalftoneFilter
+
+- (id)init;
+{
+    if (!(self = [super initWithFragmentShaderFromString:kGPUImageHalftoneFragmentShaderString]))
+    {
+		return nil;
+    }
+
+    self.fractionalWidthOfAPixel = 0.01;
+
+    return self;
+}
+
+@end