Improved the Hough transform line detector, as suggested by mabuchner…

… in Issue BradLarson#1871. Also expanded the search radius for the non-maximum suppression filter.

examples/iOS/FilterShowcase/FilterShowcase.xcodeproj/project.pbxproj

@@ -246,7 +246,7 @@
 			isa = PBXProject;
 			attributes = {
 				CLASSPREFIX = Showcase;
-				LastUpgradeCheck = 0500;
+				LastUpgradeCheck = 0610;
 				ORGANIZATIONNAME = "Cell Phone";
 				TargetAttributes = {
 					BC982B0114F046AC0001FF6F = {
@@ -368,9 +368,11 @@
 				CLANG_WARN_EMPTY_BODY = YES;
 				CLANG_WARN_ENUM_CONVERSION = YES;
 				CLANG_WARN_INT_CONVERSION = YES;
+				CLANG_WARN_UNREACHABLE_CODE = YES;
 				CLANG_WARN__DUPLICATE_METHOD_MATCH = YES;
 				"CODE_SIGN_IDENTITY[sdk=iphoneos*]" = "iPhone Developer";
 				COPY_PHASE_STRIP = NO;
+				ENABLE_STRICT_OBJC_MSGSEND = YES;
 				GCC_C_LANGUAGE_STANDARD = gnu99;
 				GCC_DYNAMIC_NO_PIC = NO;
 				GCC_OPTIMIZATION_LEVEL = 0;
@@ -408,9 +410,11 @@
 				CLANG_WARN_EMPTY_BODY = YES;
 				CLANG_WARN_ENUM_CONVERSION = YES;
 				CLANG_WARN_INT_CONVERSION = YES;
+				CLANG_WARN_UNREACHABLE_CODE = YES;
 				CLANG_WARN__DUPLICATE_METHOD_MATCH = YES;
 				"CODE_SIGN_IDENTITY[sdk=iphoneos*]" = "iPhone Developer";
 				COPY_PHASE_STRIP = YES;
+				ENABLE_STRICT_OBJC_MSGSEND = YES;
 				GCC_C_LANGUAGE_STANDARD = gnu99;
 				GCC_VERSION = com.apple.compilers.llvm.clang.1_0;
 				GCC_WARN_64_TO_32_BIT_CONVERSION = YES;

examples/iOS/FilterShowcase/FilterShowcase.xcodeproj/xcshareddata/xcschemes/FilterShowcase.xcscheme

@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <Scheme
-   LastUpgradeVersion = "0500"
+   LastUpgradeVersion = "0610"
    version = "1.3">
    <BuildAction
       parallelizeBuildables = "YES"

framework/GPUImage.xcodeproj/xcshareddata/xcschemes/Documentation.xcscheme

@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <Scheme
-   LastUpgradeVersion = "0600"
+   LastUpgradeVersion = "0610"
    version = "1.3">
    <BuildAction
       parallelizeBuildables = "YES"
@@ -39,6 +39,15 @@
       ignoresPersistentStateOnLaunch = "NO"
       debugDocumentVersioning = "YES"
       allowLocationSimulation = "YES">
+      <MacroExpansion>
+         <BuildableReference
+            BuildableIdentifier = "primary"
+            BlueprintIdentifier = "BC552B361558C6F4001F3FFA"
+            BuildableName = "Documentation"
+            BlueprintName = "Documentation"
+            ReferencedContainer = "container:GPUImage.xcodeproj">
+         </BuildableReference>
+      </MacroExpansion>
       <AdditionalOptions>
       </AdditionalOptions>
    </LaunchAction>

framework/GPUImage.xcodeproj/xcshareddata/xcschemes/GPUImage.xcscheme

@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <Scheme
-   LastUpgradeVersion = "0600"
+   LastUpgradeVersion = "0610"
    version = "1.3">
    <BuildAction
       parallelizeBuildables = "YES"
@@ -49,6 +49,15 @@
       ignoresPersistentStateOnLaunch = "NO"
       debugDocumentVersioning = "YES"
       allowLocationSimulation = "YES">
+      <MacroExpansion>
+         <BuildableReference
+            BuildableIdentifier = "primary"
+            BlueprintIdentifier = "BCF1A33314DDB1EC00852800"
+            BuildableName = "libGPUImage.a"
+            BlueprintName = "GPUImage"
+            ReferencedContainer = "container:GPUImage.xcodeproj">
+         </BuildableReference>
+      </MacroExpansion>
       <AdditionalOptions>
       </AdditionalOptions>
    </LaunchAction>

framework/GPUImage.xcodeproj/xcshareddata/xcschemes/GPUImageFramework.xcscheme

@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <Scheme
-   LastUpgradeVersion = "0600"
+   LastUpgradeVersion = "0610"
    version = "2.0">
    <BuildAction
       parallelizeBuildables = "YES"
@@ -40,6 +40,15 @@
       debugDocumentVersioning = "YES"
       debugXPCServices = "NO"
       allowLocationSimulation = "YES">
+      <MacroExpansion>
+         <BuildableReference
+            BuildableIdentifier = "primary"
+            BlueprintIdentifier = "BCE209E41943F20C002FEED8"
+            BuildableName = "GPUImage.framework"
+            BlueprintName = "GPUImageFramework"
+            ReferencedContainer = "container:GPUImage.xcodeproj">
+         </BuildableReference>
+      </MacroExpansion>
       <AdditionalOptions>
       </AdditionalOptions>
    </LaunchAction>

framework/Source/GPUImageHoughTransformLineDetector.m

@@ -20,49 +20,27 @@ - (id)init;
 		return nil;
     }
 
-#ifdef DEBUGLINEDETECTION
-    _intermediateImages = [[NSMutableArray alloc] init];
-#endif
-
     // First pass: do edge detection and threshold that to just have white pixels for edges
 //    if ([GPUImageContext deviceSupportsFramebufferReads])
 //    if ([GPUImageContext deviceSupportsFramebufferReads])
 //    {
-        thresholdEdgeDetectionFilter = [[GPUImageThresholdEdgeDetectionFilter alloc] init];
+//        thresholdEdgeDetectionFilter = [[GPUImageThresholdEdgeDetectionFilter alloc] init];
 //        thresholdEdgeDetectionFilter = [[GPUImageSobelEdgeDetectionFilter alloc] init];
-        [(GPUImageThresholdEdgeDetectionFilter *)thresholdEdgeDetectionFilter setThreshold:0.4];
+//        [(GPUImageThresholdEdgeDetectionFilter *)thresholdEdgeDetectionFilter setThreshold:0.07];
 //        [(GPUImageThresholdEdgeDetectionFilter *)thresholdEdgeDetectionFilter setEdgeStrength:0.25];
-        [(GPUImageThresholdEdgeDetectionFilter *)thresholdEdgeDetectionFilter setEdgeStrength:1.0];
+//        [(GPUImageThresholdEdgeDetectionFilter *)thresholdEdgeDetectionFilter setEdgeStrength:1.0];
 //        thresholdEdgeDetectionFilter = [[GPUImageCannyEdgeDetectionFilter alloc] init];
 //    }
 //    else
 //    {
-//        thresholdEdgeDetectionFilter = [[GPUImageCannyEdgeDetectionFilter alloc] init];
+        thresholdEdgeDetectionFilter = [[GPUImageCannyEdgeDetectionFilter alloc] init];
 //    }
     [self addFilter:thresholdEdgeDetectionFilter];
 
-#ifdef DEBUGLINEDETECTION
-    __unsafe_unretained NSMutableArray *weakIntermediateImages = _intermediateImages;
-    __unsafe_unretained GPUImageOutput<GPUImageInput> *weakFilter = thresholdEdgeDetectionFilter;
-    [thresholdEdgeDetectionFilter setFrameProcessingCompletionBlock:^(GPUImageOutput *filter, CMTime frameTime){
-        [weakIntermediateImages removeAllObjects];
-        UIImage *intermediateImage = [weakFilter imageFromCurrentlyProcessedOutput];
-        [weakIntermediateImages addObject:intermediateImage];
-    }];
-#endif
-
     // Second pass: extract the white points and draw representative lines in parallel coordinate space
     parallelCoordinateLineTransformFilter = [[GPUImageParallelCoordinateLineTransformFilter alloc] init];
     [self addFilter:parallelCoordinateLineTransformFilter];
 
-#ifdef DEBUGLINEDETECTION
-    weakFilter = parallelCoordinateLineTransformFilter;
-    [parallelCoordinateLineTransformFilter setFrameProcessingCompletionBlock:^(GPUImageOutput *filter, CMTime frameTime){
-        UIImage *intermediateImage = [weakFilter imageFromCurrentlyProcessedOutput];
-        [weakIntermediateImages addObject:intermediateImage];
-    }];
-#endif
-
     // Third pass: apply non-maximum suppression
     if ([GPUImageContext deviceSupportsFramebufferReads])
     {
@@ -76,12 +54,27 @@ - (id)init;
 
     __unsafe_unretained GPUImageHoughTransformLineDetector *weakSelf = self;
 #ifdef DEBUGLINEDETECTION
-    weakFilter = nonMaximumSuppressionFilter;
-    [nonMaximumSuppressionFilter setFrameProcessingCompletionBlock:^(GPUImageOutput *filter, CMTime frameTime){
+    _intermediateImages = [[NSMutableArray alloc] init];
+    __unsafe_unretained NSMutableArray *weakIntermediateImages = _intermediateImages;
 
-        UIImage *intermediateImage = [weakFilter imageFromCurrentlyProcessedOutput];
+//    __unsafe_unretained GPUImageOutput<GPUImageInput> *weakEdgeDetectionFilter = thresholdEdgeDetectionFilter;
+//    [thresholdEdgeDetectionFilter setFrameProcessingCompletionBlock:^(GPUImageOutput *filter, CMTime frameTime){
+//        [weakIntermediateImages removeAllObjects];
+//        UIImage *intermediateImage = [weakEdgeDetectionFilter imageFromCurrentFramebuffer];
+//        [weakIntermediateImages addObject:intermediateImage];
+//    }];
+//
+//    __unsafe_unretained GPUImageOutput<GPUImageInput> *weakParallelCoordinateLineTransformFilter = parallelCoordinateLineTransformFilter;
+//    [parallelCoordinateLineTransformFilter setFrameProcessingCompletionBlock:^(GPUImageOutput *filter, CMTime frameTime){
+//        UIImage *intermediateImage = [weakParallelCoordinateLineTransformFilter imageFromCurrentFramebuffer];
+//        [weakIntermediateImages addObject:intermediateImage];
+//    }];
+
+    __unsafe_unretained GPUImageOutput<GPUImageInput> *weakNonMaximumSuppressionFilter = nonMaximumSuppressionFilter;
+    [nonMaximumSuppressionFilter setFrameProcessingCompletionBlock:^(GPUImageOutput *filter, CMTime frameTime){
+        UIImage *intermediateImage = [weakNonMaximumSuppressionFilter imageFromCurrentFramebuffer];
         [weakIntermediateImages addObject:intermediateImage];
-        
+
         [weakSelf extractLineParametersFromImageAtFrameTime:frameTime];
     }];
 #else
@@ -98,7 +91,7 @@ - (id)init;
     self.terminalFilter = nonMaximumSuppressionFilter;
 
 //    self.edgeThreshold = 0.95;
-    self.lineDetectionThreshold = 0.8;
+    self.lineDetectionThreshold = 0.12;
 
     return self;
 }
@@ -137,15 +130,21 @@ - (void)extractLineParametersFromImageAtFrameTime:(CMTime)frameTime;
 
     unsigned int currentByte = 0;
     unsigned int cornerStorageIndex = 0;
+    unsigned long lineStrengthCounter = 0;
     while (currentByte < imageByteSize)
     {
         GLubyte colorByte = rawImagePixels[currentByte];
+//        NSLog(@"(%d,%d): [%d,%d,%d,%d]", xCoordinate, yCoordinate, rawImagePixels[currentByte], rawImagePixels[currentByte+1], rawImagePixels[currentByte+2], rawImagePixels[currentByte+3]);
+//        NSLog(@"[%d,%d,%d,%d]", rawImagePixels[currentByte], rawImagePixels[currentByte+1], rawImagePixels[currentByte+2], rawImagePixels[currentByte+3]);
 
         if (colorByte > 0)
         {
             unsigned int xCoordinate = currentByte % imageWidth;
             unsigned int yCoordinate = currentByte / imageWidth;
 
+            lineStrengthCounter += colorByte;
+//            NSLog(@"(%d,%d): [%d,%d,%d,%d]", xCoordinate, yCoordinate, rawImagePixels[currentByte], rawImagePixels[currentByte+1], rawImagePixels[currentByte+2], rawImagePixels[currentByte+3]);
+
             CGFloat normalizedXCoordinate = -1.0 + 2.0 * (CGFloat)(xCoordinate / 4) / imageSize.width;
             CGFloat normalizedYCoordinate = -1.0 + 2.0 * (CGFloat)(yCoordinate) / imageSize.height;
 
@@ -192,7 +191,7 @@ - (void)extractLineParametersFromImageAtFrameTime:(CMTime)frameTime;
 
 //    CFAbsoluteTime currentFrameTime = (CFAbsoluteTimeGetCurrent() - startTime);
 //    NSLog(@"Processing time : %f ms", 1000.0 * currentFrameTime);
-    
+
     if (linesDetectedBlock != NULL)
     {
         linesDetectedBlock(linesArray, numberOfLines, frameTime);
@@ -208,17 +207,15 @@ - (BOOL)wantsMonochromeInput;
 #pragma mark -
 #pragma mark Accessors
 
-/*
-- (void)setEdgeThreshold:(CGFloat)newValue;
-{
-    thresholdEdgeDetectionFilter.threshold = newValue;
-}
-
-- (CGFloat)edgeThreshold;
-{
-    return thresholdEdgeDetectionFilter.threshold;
-}
- */
+//- (void)setEdgeThreshold:(CGFloat)newValue;
+//{
+//    [(GPUImageCannyEdgeDetectionFilter *)thresholdEdgeDetectionFilter setThreshold:newValue];
+//}
+//
+//- (CGFloat)edgeThreshold;
+//{
+//    return [(GPUImageCannyEdgeDetectionFilter *)thresholdEdgeDetectionFilter threshold];
+//}
 
 - (void)setLineDetectionThreshold:(CGFloat)newValue;
 {
@@ -230,4 +227,15 @@ - (CGFloat)lineDetectionThreshold;
     return nonMaximumSuppressionFilter.threshold;
 }
 
+#ifdef DEBUGLINEDETECTION
+- (void)newFrameReadyAtTime:(CMTime)frameTime atIndex:(NSInteger)textureIndex;
+{
+//    [thresholdEdgeDetectionFilter useNextFrameForImageCapture];
+//    [parallelCoordinateLineTransformFilter useNextFrameForImageCapture];
+    [nonMaximumSuppressionFilter useNextFrameForImageCapture];
+
+    [super newFrameReadyAtTime:frameTime atIndex:textureIndex];
+}
+#endif
+
 @end

framework/Source/GPUImageNonMaximumSuppressionFilter.m

@@ -31,9 +31,9 @@ void main()
 
      // Use a tiebreaker for pixels to the left and immediately above this one
      lowp float multiplier = 1.0 - step(centerColor.r, topColor);
-     multiplier = multiplier * 1.0 - step(centerColor.r, topLeftColor);
-     multiplier = multiplier * 1.0 - step(centerColor.r, leftColor);
-     multiplier = multiplier * 1.0 - step(centerColor.r, bottomLeftColor);
+     multiplier = multiplier * (1.0 - step(centerColor.r, topLeftColor));
+     multiplier = multiplier * (1.0 - step(centerColor.r, leftColor));
+     multiplier = multiplier * (1.0 - step(centerColor.r, bottomLeftColor));
 
      lowp float maxValue = max(centerColor.r, bottomColor);
      maxValue = max(maxValue, bottomRightColor);
@@ -74,9 +74,9 @@ void main()
 
      // Use a tiebreaker for pixels to the left and immediately above this one
      float multiplier = 1.0 - step(centerColor.r, topColor);
-     multiplier = multiplier * 1.0 - step(centerColor.r, topLeftColor);
-     multiplier = multiplier * 1.0 - step(centerColor.r, leftColor);
-     multiplier = multiplier * 1.0 - step(centerColor.r, bottomLeftColor);
+     multiplier = multiplier * (1.0 - step(centerColor.r, topLeftColor));
+     multiplier = multiplier * (1.0 - step(centerColor.r, leftColor));
+     multiplier = multiplier * (1.0 - step(centerColor.r, bottomLeftColor));
 
      float maxValue = max(centerColor.r, bottomColor);
      maxValue = max(maxValue, bottomRightColor);

framework/Source/GPUImageParallelCoordinateLineTransformFilter.m

@@ -25,8 +25,8 @@ void main()
 // NOTE: See below for where I'm tacking on the required extension as a prefix
 NSString *const kGPUImageHoughAccumulationFBOReadFragmentShaderString = SHADER_STRING
 (
-// const lowp float scalingFactor = 0.004;
- const lowp float scalingFactor = 0.1;
+ const lowp float scalingFactor = 0.004;
+// const lowp float scalingFactor = 0.1;
 
  void main()
  {
@@ -149,10 +149,12 @@ - (void)renderToTextureWithVertices:(const GLfloat *)vertices textureCoordinates
         return;
     }
 
-    [GPUImageContext useImageProcessingContext];
-
     // Grab the edge points from the previous frame and create the parallel coordinate lines for them
     // This would be a great place to have a working histogram pyramid implementation
+
+    [GPUImageContext useImageProcessingContext];
+    [firstInputFramebuffer activateFramebuffer];
+
     glFinish();
     glReadPixels(0, 0, inputTextureSize.width, inputTextureSize.height, GL_RGBA, GL_UNSIGNED_BYTE, rawImagePixels);
 
@@ -223,9 +225,15 @@ - (void)renderToTextureWithVertices:(const GLfloat *)vertices textureCoordinates
 
     outputFramebuffer = [[GPUImageContext sharedFramebufferCache] fetchFramebufferForSize:[self sizeOfFBO] textureOptions:self.outputTextureOptions onlyTexture:NO];
     [outputFramebuffer activateFramebuffer];
-
+
+    if (usingNextFrameForImageCapture)
+    {
+        [outputFramebuffer lock];
+    }
+
     [GPUImageContext setActiveShaderProgram:filterProgram];
-
+    [self setUniformsForProgramAtIndex:0];
+
     glClearColor(0.0, 0.0, 0.0, 1.0);
     glClear(GL_COLOR_BUFFER_BIT);
 
@@ -237,9 +245,10 @@ - (void)renderToTextureWithVertices:(const GLfloat *)vertices textureCoordinates
     }
     else
     {
-        glLineWidth(1);
     }
-
+
+    glLineWidth(1);
+
 	glVertexAttribPointer(filterPositionAttribute, 2, GL_FLOAT, 0, 0, lineCoordinates);
     glDrawArrays(GL_LINES, 0, (linePairsToRender * 4));
 
@@ -248,6 +257,10 @@ - (void)renderToTextureWithVertices:(const GLfloat *)vertices textureCoordinates
         glDisable(GL_BLEND);
     }
     [firstInputFramebuffer unlock];
+    if (usingNextFrameForImageCapture)
+    {
+        dispatch_semaphore_signal(imageCaptureSemaphore);
+    }
 }
 
 @end