Added an image buffet filter that delays frames, allowing for comparative processing of sequential frames. There are some slight issues with timing on the blends that I still need to fix.

Author: BradLarson

examples/FilterShowcase/FilterShowcase/ShowcaseFilterListController.m

@@ -92,6 +92,7 @@ - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(N
 		case GPUIMAGE_HARRISCORNERDETECTION: cell.textLabel.text = @"Harris corner detection"; break;
 		case GPUIMAGE_NOBLECORNERDETECTION: cell.textLabel.text = @"Noble corner detection"; break;
 		case GPUIMAGE_SHITOMASIFEATUREDETECTION: cell.textLabel.text = @"Shi-Tomasi feature detection"; break;
+		case GPUIMAGE_BUFFER: cell.textLabel.text = @"Image buffer"; break;
 		case GPUIMAGE_SKETCH: cell.textLabel.text = @"Sketch"; break;
 		case GPUIMAGE_TOON: cell.textLabel.text = @"Toon"; break;
 		case GPUIMAGE_SMOOTHTOON: cell.textLabel.text = @"Smooth toon"; break;

examples/FilterShowcase/FilterShowcase/ShowcaseFilterViewController.h

@@ -33,6 +33,7 @@ typedef enum {
     GPUIMAGE_HARRISCORNERDETECTION,
     GPUIMAGE_NOBLECORNERDETECTION,
     GPUIMAGE_SHITOMASIFEATUREDETECTION,
+    GPUIMAGE_BUFFER,
     GPUIMAGE_SKETCH,
     GPUIMAGE_TOON,
     GPUIMAGE_SMOOTHTOON,

examples/FilterShowcase/FilterShowcase/ShowcaseFilterViewController.m

@@ -398,7 +398,13 @@ - (void)setupFilter;
 
             filter = [[GPUImageCannyEdgeDetectionFilter alloc] init];
         }; break;
-
+        case GPUIMAGE_BUFFER:
+        {
+            self.title = @"Image Buffer";
+            self.filterSettingsSlider.hidden = YES;
+            
+            filter = [[GPUImageBuffer alloc] init];
+        }; break;
         case GPUIMAGE_SKETCH:
         {
             self.title = @"Sketch";
@@ -982,6 +988,25 @@ - (void)setupFilter;
                 [weakUIElementInput update];
             }];
         }
+        else if (filterType == GPUIMAGE_BUFFER)
+        {
+            
+            GPUImageDifferenceBlendFilter *blendFilter = [[GPUImageDifferenceBlendFilter alloc] init];
+            [blendFilter forceProcessingAtSize:CGSizeMake(480.0, 640.0)];
+
+//            [filter addTarget:filterView];            
+            [videoCamera removeTarget:filter];
+
+            GPUImageGammaFilter *gammaFilter = [[GPUImageGammaFilter alloc] init];
+            [videoCamera addTarget:gammaFilter];
+            [gammaFilter addTarget:blendFilter];
+            gammaFilter.targetToIgnoreForUpdates = blendFilter;
+            [videoCamera addTarget:filter];
+
+            [filter addTarget:blendFilter];
+            
+            [blendFilter addTarget:filterView];
+        }
         else 
         {
             [filter addTarget:filterView];

framework/GPUImage.xcodeproj/project.pbxproj

@@ -190,6 +190,8 @@
 		BCB6B9051507CA8D0041703B /* GPUImageCropFilter.m in Sources */ = {isa = PBXBuildFile; fileRef = BCB6B9031507CA8C0041703B /* GPUImageCropFilter.m */; };
 		BCBCE9991595021B00E0ED33 /* GPUImageMonochromeFilter.h in Headers */ = {isa = PBXBuildFile; fileRef = BCBCE9971595021B00E0ED33 /* GPUImageMonochromeFilter.h */; };
 		BCBCE99A1595021B00E0ED33 /* GPUImageMonochromeFilter.m in Sources */ = {isa = PBXBuildFile; fileRef = BCBCE9981595021B00E0ED33 /* GPUImageMonochromeFilter.m */; };
+		BCBCE9D5159944AC00E0ED33 /* GPUImageBuffer.h in Headers */ = {isa = PBXBuildFile; fileRef = BCBCE9D3159944AB00E0ED33 /* GPUImageBuffer.h */; };
+		BCBCE9D6159944AC00E0ED33 /* GPUImageBuffer.m in Sources */ = {isa = PBXBuildFile; fileRef = BCBCE9D4159944AB00E0ED33 /* GPUImageBuffer.m */; };
 		BCC11D72154B44DC0044F5A0 /* GPUImageHistogramGenerator.h in Headers */ = {isa = PBXBuildFile; fileRef = BCC11D70154B44DC0044F5A0 /* GPUImageHistogramGenerator.h */; };
 		BCC11D73154B44DC0044F5A0 /* GPUImageHistogramGenerator.m in Sources */ = {isa = PBXBuildFile; fileRef = BCC11D71154B44DC0044F5A0 /* GPUImageHistogramGenerator.m */; };
 		BCC1E5A8151E74B20006EFA5 /* GPUImagePosterizeFilter.h in Headers */ = {isa = PBXBuildFile; fileRef = BCC1E5A6151E74B20006EFA5 /* GPUImagePosterizeFilter.h */; };
@@ -440,6 +442,8 @@
 		BCB6B9031507CA8C0041703B /* GPUImageCropFilter.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; name = GPUImageCropFilter.m; path = Source/GPUImageCropFilter.m; sourceTree = SOURCE_ROOT; };
 		BCBCE9971595021B00E0ED33 /* GPUImageMonochromeFilter.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; name = GPUImageMonochromeFilter.h; path = Source/GPUImageMonochromeFilter.h; sourceTree = SOURCE_ROOT; };
 		BCBCE9981595021B00E0ED33 /* GPUImageMonochromeFilter.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; name = GPUImageMonochromeFilter.m; path = Source/GPUImageMonochromeFilter.m; sourceTree = SOURCE_ROOT; };
+		BCBCE9D3159944AB00E0ED33 /* GPUImageBuffer.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; name = GPUImageBuffer.h; path = Source/GPUImageBuffer.h; sourceTree = SOURCE_ROOT; };
+		BCBCE9D4159944AB00E0ED33 /* GPUImageBuffer.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; name = GPUImageBuffer.m; path = Source/GPUImageBuffer.m; sourceTree = SOURCE_ROOT; };
 		BCC11D70154B44DC0044F5A0 /* GPUImageHistogramGenerator.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; name = GPUImageHistogramGenerator.h; path = Source/GPUImageHistogramGenerator.h; sourceTree = SOURCE_ROOT; };
 		BCC11D71154B44DC0044F5A0 /* GPUImageHistogramGenerator.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; name = GPUImageHistogramGenerator.m; path = Source/GPUImageHistogramGenerator.m; sourceTree = SOURCE_ROOT; };
 		BCC1E5A6151E74B20006EFA5 /* GPUImagePosterizeFilter.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; name = GPUImagePosterizeFilter.h; path = Source/GPUImagePosterizeFilter.h; sourceTree = SOURCE_ROOT; };
@@ -684,6 +688,8 @@
 				BCC1E5B7151E83700006EFA5 /* GPUImageFilterGroup.m */,
 				BC01E830155CA5E1004C75C3 /* GPUImage3x3TextureSamplingFilter.h */,
 				BC01E831155CA5E1004C75C3 /* GPUImage3x3TextureSamplingFilter.m */,
+				BCBCE9D3159944AB00E0ED33 /* GPUImageBuffer.h */,
+				BCBCE9D4159944AB00E0ED33 /* GPUImageBuffer.m */,
 				BC1B715D14F4AFFF00ACA2AB /* Color processing */,
 				BCC93A5215031B1700958B26 /* Image processing */,
 				BC1B715E14F4B04800ACA2AB /* Blends */,
@@ -1005,6 +1011,7 @@
 				BC0690F7157C5075009274F9 /* GPUImageColorPackingFilter.h in Headers */,
 				BC76CE9B15813818008B45D3 /* GPUImageSphereRefractionFilter.h in Headers */,
 				BCBCE9991595021B00E0ED33 /* GPUImageMonochromeFilter.h in Headers */,
+				BCBCE9D5159944AC00E0ED33 /* GPUImageBuffer.h in Headers */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};
@@ -1230,6 +1237,7 @@
 				BC0690F8157C5075009274F9 /* GPUImageColorPackingFilter.m in Sources */,
 				BC76CE9C15813818008B45D3 /* GPUImageSphereRefractionFilter.m in Sources */,
 				BCBCE99A1595021B00E0ED33 /* GPUImageMonochromeFilter.m in Sources */,
+				BCBCE9D6159944AC00E0ED33 /* GPUImageBuffer.m in Sources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};

framework/Source/GPUImage.h

@@ -16,6 +16,7 @@
 #import "GPUImageFilterGroup.h"
 #import "GPUImageTextureInput.h"
 #import "GPUImageUIElement.h"
+#import "GPUImageBuffer.h"
 
 // Filters
 #import "GPUImageFilter.h"

framework/Source/GPUImageBuffer.h

@@ -0,0 +1,10 @@
+#import "GPUImageFilter.h"
+
+@interface GPUImageBuffer : GPUImageFilter
+{
+    NSMutableArray *bufferedTextures;
+}
+
+@property(readwrite, nonatomic) NSUInteger bufferSize;
+
+@end

framework/Source/GPUImageBuffer.m

@@ -0,0 +1,164 @@
+#import "GPUImageBuffer.h"
+
+@implementation GPUImageBuffer
+
+@synthesize bufferSize = _bufferSize;
+
+#pragma mark -
+#pragma mark Initialization and teardown
+
+- (id)init;
+{
+    if (!(self = [self initWithFragmentShaderFromString:kGPUImagePassthroughFragmentShaderString]))
+    {
+        return nil;
+    }
+    
+    bufferedTextures = [[NSMutableArray alloc] init];
+    [bufferedTextures addObject:[NSNumber numberWithInt:outputTexture]];
+    _bufferSize = 1;
+    
+    return self;
+}
+
+- (void)dealloc
+{
+    for (NSNumber *currentTextureName in bufferedTextures)
+    {
+        [self removeTexture:[currentTextureName intValue]];
+    }
+}
+
+#pragma mark -
+#pragma mark GPUImageInput
+
+- (void)newFrameReadyAtTime:(CMTime)frameTime;
+{
+    static const GLfloat imageVertices[] = {
+        -1.0f, -1.0f,
+        1.0f, -1.0f,
+        -1.0f,  1.0f,
+        1.0f,  1.0f,
+    };
+
+    // Let the downstream video elements see the previous frame from the buffer before rendering a new one into place
+    [self informTargetsAboutNewFrameAtTime:frameTime];
+    
+    // Move the last frame to the back of the buffer, if needed
+    if (_bufferSize > 1)
+    {
+        NSNumber *lastTextureName = [bufferedTextures objectAtIndex:0];
+        [bufferedTextures removeObjectAtIndex:0];
+        [bufferedTextures addObject:lastTextureName];
+    }
+    else
+    {
+        // Make sure the previous rendering has finished before enqueuing the current frame when simply delaying by one frame
+        glFinish();
+    }    
+    
+    // Render the new frame to the back of the buffer
+    [self renderToTextureWithVertices:imageVertices textureCoordinates:[[self class] textureCoordinatesForRotation:inputRotation] sourceTexture:filterSourceTexture];
+}
+
+- (void)renderToTextureWithVertices:(const GLfloat *)vertices textureCoordinates:(const GLfloat *)textureCoordinates sourceTexture:(GLuint)sourceTexture;
+{
+    if (self.preventRendering)
+    {
+        return;
+    }
+    
+    [GPUImageOpenGLESContext useImageProcessingContext];
+    [self setFilterFBO];
+    
+    glBindTexture(GL_TEXTURE_2D, [[bufferedTextures lastObject] intValue]);
+    glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, [[bufferedTextures lastObject] intValue], 0);
+    
+    [filterProgram use];
+    
+    glClearColor(backgroundColorRed, backgroundColorGreen, backgroundColorBlue, backgroundColorAlpha);
+    glClear(GL_COLOR_BUFFER_BIT);
+    
+	glActiveTexture(GL_TEXTURE2);
+	glBindTexture(GL_TEXTURE_2D, sourceTexture);
+	
+	glUniform1i(filterInputTextureUniform, 2);	
+    
+    glVertexAttribPointer(filterPositionAttribute, 2, GL_FLOAT, 0, 0, vertices);
+	glVertexAttribPointer(filterTextureCoordinateAttribute, 2, GL_FLOAT, 0, 0, textureCoordinates);
+    
+    glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);    
+}
+
+- (void)prepareForImageCapture;
+{
+    // Disable this for now, until I figure out how to integrate the texture caches with a buffer like this
+}
+
+#pragma mark -
+#pragma mark Managing targets
+
+- (void)setInputTextureForTarget:(id<GPUImageInput>)target atIndex:(NSInteger)inputTextureIndex;
+{
+    [target setInputTexture:[[bufferedTextures objectAtIndex:0] intValue] atIndex:inputTextureIndex];
+}
+
+
+#pragma mark -
+#pragma mark Texture management
+
+- (GLuint)generateTexture;
+{
+    GLuint newTextureName = 0;
+    glActiveTexture(GL_TEXTURE0);
+    glGenTextures(1, &newTextureName);
+	glBindTexture(GL_TEXTURE_2D, newTextureName);
+	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
+	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
+	// This is necessary for non-power-of-two textures
+	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
+	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
+
+    CGSize currentFBOSize = [self sizeOfFBO];
+    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, (int)currentFBOSize.width, (int)currentFBOSize.height, 0, GL_RGBA, GL_UNSIGNED_BYTE, 0);
+    glBindTexture(GL_TEXTURE_2D, 0);
+
+    return newTextureName;
+}
+
+- (void)removeTexture:(GLuint)textureToRemove;
+{
+    glDeleteTextures(1, &textureToRemove);
+}
+
+#pragma mark -
+#pragma mark Accessors
+
+- (void)setBufferSize:(NSUInteger)newValue;
+{
+    if ( (newValue == _bufferSize) || (newValue < 1) )
+    {
+        return;
+    }
+        
+    if (newValue > _bufferSize)
+    {
+        NSUInteger texturesToAdd = newValue - _bufferSize;
+        for (NSUInteger currentTextureIndex = 0; currentTextureIndex < texturesToAdd; currentTextureIndex++)
+        {
+            [bufferedTextures addObject:[NSNumber numberWithInt:[self generateTexture]]];
+        }
+    }
+    else
+    {
+        NSUInteger texturesToRemove = _bufferSize - newValue;
+        for (NSUInteger currentTextureIndex = 0; currentTextureIndex < texturesToRemove; currentTextureIndex++)
+        {
+            NSNumber *lastTextureName = [bufferedTextures lastObject];
+            [bufferedTextures removeObjectAtIndex:([bufferedTextures count] - 1)];
+            [self removeTexture:[lastTextureName intValue]];
+        }
+    }
+}
+
+@end

framework/Source/GPUImageMovie.m

@@ -48,6 +48,14 @@ - (id)initWithURL:(NSURL *)url;
     return self;
 }
 
+- (void)dealloc
+{
+    if ([GPUImageOpenGLESContext supportsFastTextureUpload])
+    {
+        CFRelease(coreVideoTextureCache);
+    }
+}
+
 #pragma mark -
 #pragma mark Movie processing
 

framework/Source/GPUImageMovieWriter.m

@@ -401,7 +401,7 @@ - (void)renderAtInternalSize;
 
     glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
 
-    glFlush();
+    glFinish();
 }
 
 #pragma mark -

framework/Source/GPUImagePicture.h

@@ -4,7 +4,7 @@
 
 @interface GPUImagePicture : GPUImageOutput
 {
-    UIImage *imageSource;    
+    CGSize pixelSizeOfImage;
 }
 
 // Initialization and teardown