GPUImage源码解读(七)

  • GPUImagePicture

从名称就可以知道GPUImagePicture是GPUImage框架中处理与图片相关的类,它的主要作用是将UIImage或CGImage转化为纹理对象。GPUImagePicture继承自GPUImageOutput,从而可以知道它能够作为输出,由于它没有实现GPUImageInput协议,不能处理输入。因此,常常作为响应链源。

初始化方法 ,所有初始化方法最后都会调用最后一个初始化方法

// Initialization and teardown
// 通过图片URL初始化
- (id)initWithURL:(NSURL *)url;
// 通过UIImage或CGImage初始化
- (id)initWithImage:(UIImage *)newImageSource;
- (id)initWithCGImage:(CGImageRef)newImageSource;
// 通过UIImage或CGImage、是否平滑缩放、是否去除预乘alpha来初始化
- (id)initWithImage:(UIImage *)newImageSource smoothlyScaleOutput:(BOOL)smoothlyScaleOutput;
- (id)initWithCGImage:(CGImageRef)newImageSource smoothlyScaleOutput:(BOOL)smoothlyScaleOutput;//所有初始化方法最后都会调用这个方法
  • 实现方法

- (id)initWithCGImage:(CGImageRef)newImageSource smoothlyScaleOutput:(BOOL)smoothlyScaleOutput;
{
if (!(self = [super init]))
{
return nil;
}
hasProcessedImage = NO;
self.shouldSmoothlyScaleOutput = smoothlyScaleOutput;
imageUpdateSemaphore = dispatch_semaphore_create(0);
dispatch_semaphore_signal(imageUpdateSemaphore);
//1获取图片适合的宽高(不能超出OpenGL ES允许的最大纹理宽高)
// TODO: Dispatch this whole thing asynchronously to move image loading off main thread
CGFloat widthOfImage = CGImageGetWidth(newImageSource);
CGFloat heightOfImage = CGImageGetHeight(newImageSource);
// If passed an empty image reference, CGContextDrawImage will fail in future versions of the SDK.
NSAssert( widthOfImage > 0 && heightOfImage > 0, @"Passed image must not be empty - it should be at least 1px tall and wide");
pixelSizeOfImage = CGSizeMake(widthOfImage, heightOfImage);
CGSize pixelSizeToUseForTexture = pixelSizeOfImage;
//是否要重绘
BOOL shouldRedrawUsingCoreGraphics = NO;
// For now, deal with images larger than the maximum texture size by resizing to be within that limit
//openglES 允许的最大值
CGSize scaledImageSizeToFitOnGPU = [GPUImageContext sizeThatFitsWithinATextureForSize:pixelSizeOfImage];
if (!CGSizeEqualToSize(scaledImageSizeToFitOnGPU, pixelSizeOfImage))
{
pixelSizeOfImage = scaledImageSizeToFitOnGPU;
pixelSizeToUseForTexture = pixelSizeOfImage;
shouldRedrawUsingCoreGraphics = YES;
}
//
if (self.shouldSmoothlyScaleOutput)
{
//2如果使用了smoothlyScaleOutput,需要调整宽高为接近2的幂的值,调整后必须重绘; log2=0.3010 ceil:如果参数是小数,则求最小的整数但不小于本身. @see round:如果参数是小数,则求本身的四舍五入。floor:如果参数是小数,则求最大的整数但不大于本身.
// In order to use mipmaps, you need to provide power-of-two textures, so convert to the next largest power of two and stretch to fill
CGFloat powerClosestToWidth = ceil(log2(pixelSizeOfImage.width));
CGFloat powerClosestToHeight = ceil(log2(pixelSizeOfImage.height));
pixelSizeToUseForTexture = CGSizeMake(pow(2.0, powerClosestToWidth), pow(2.0, powerClosestToHeight));
shouldRedrawUsingCoreGraphics = YES;
}
GLubyte *imageData = NULL;
CFDataRef dataFromImageDataProvider = NULL;
GLenum format = GL_BGRA;
//3如果不用重绘,则获取大小、alpha等信息;
if (!shouldRedrawUsingCoreGraphics) {
/* Check that the memory layout is compatible with GL, as we cannot use glPixelStore to
* tell GL about the memory layout with GLES.
*/
//CGImageGetBytesPerRow 每行的字节数 CGImageGetBitsPerPixel每个像素的位数 CGImageGetBitsPerComponent 每个字节的组成部分
//RGBA格式不符合就要重绘
if (CGImageGetBytesPerRow(newImageSource) != CGImageGetWidth(newImageSource) * 4 ||
CGImageGetBitsPerPixel(newImageSource) != 32 ||
CGImageGetBitsPerComponent(newImageSource) != 8)
{
shouldRedrawUsingCoreGraphics = YES;
} else {
/* Check that the bitmap pixel format is compatible with GL */
//位图的组成部分信息
CGBitmapInfo bitmapInfo = CGImageGetBitmapInfo(newImageSource);
if ((bitmapInfo & kCGBitmapFloatComponents) != 0) {
/* We don't support float components for use directly in GL */
shouldRedrawUsingCoreGraphics = YES;
} else {
CGBitmapInfo byteOrderInfo = bitmapInfo & kCGBitmapByteOrderMask;
if (byteOrderInfo == kCGBitmapByteOrder32Little) {
/* Little endian, for alpha-first we can use this bitmap directly in GL */
CGImageAlphaInfo alphaInfo = bitmapInfo & kCGBitmapAlphaInfoMask;
if (alphaInfo != kCGImageAlphaPremultipliedFirst && alphaInfo != kCGImageAlphaFirst &&
alphaInfo != kCGImageAlphaNoneSkipFirst) {
shouldRedrawUsingCoreGraphics = YES;
}
} else if (byteOrderInfo == kCGBitmapByteOrderDefault || byteOrderInfo == kCGBitmapByteOrder32Big) {
/* Big endian, for alpha-last we can use this bitmap directly in GL */
CGImageAlphaInfo alphaInfo = bitmapInfo & kCGBitmapAlphaInfoMask;
if (alphaInfo != kCGImageAlphaPremultipliedLast && alphaInfo != kCGImageAlphaLast &&
alphaInfo != kCGImageAlphaNoneSkipLast) {
shouldRedrawUsingCoreGraphics = YES;
} else {
/* Can access directly using GL_RGBA pixel format */
format = GL_RGBA;
}
}
}
}
}
// CFAbsoluteTime elapsedTime, startTime = CFAbsoluteTimeGetCurrent();
//4需要重绘,则使用CoreGraphics重绘
if (shouldRedrawUsingCoreGraphics)
{
// For resized or incompatible image: redraw
imageData = (GLubyte *) calloc(1, (int)pixelSizeToUseForTexture.width * (int)pixelSizeToUseForTexture.height * 4);
CGColorSpaceRef genericRGBColorspace = CGColorSpaceCreateDeviceRGB();
CGContextRef imageContext = CGBitmapContextCreate(imageData, (size_t)pixelSizeToUseForTexture.width, (size_t)pixelSizeToUseForTexture.height, 8, (size_t)pixelSizeToUseForTexture.width * 4, genericRGBColorspace, kCGBitmapByteOrder32Little | kCGImageAlphaPremultipliedFirst);
// CGContextSetBlendMode(imageContext, kCGBlendModeCopy); // From Technical Q&A QA1708: http://developer.apple.com/library/ios/#qa/qa1708/_index.html
CGContextDrawImage(imageContext, CGRectMake(0.0, 0.0, pixelSizeToUseForTexture.width, pixelSizeToUseForTexture.height), newImageSource);
CGContextRelease(imageContext);
CGColorSpaceRelease(genericRGBColorspace);
}
else
{
// Access the raw image bytes directly
dataFromImageDataProvider = CGDataProviderCopyData(CGImageGetDataProvider(newImageSource));
imageData = (GLubyte *)CFDataGetBytePtr(dataFromImageDataProvider);
}
// elapsedTime = (CFAbsoluteTimeGetCurrent() - startTime) * 1000.0;
// NSLog(@"Core Graphics drawing time: %f", elapsedTime);
// CGFloat currentRedTotal = 0.0f, currentGreenTotal = 0.0f, currentBlueTotal = 0.0f, currentAlphaTotal = 0.0f;
// NSUInteger totalNumberOfPixels = round(pixelSizeToUseForTexture.width * pixelSizeToUseForTexture.height);
//
// for (NSUInteger currentPixel = 0; currentPixel < totalNumberOfPixels; currentPixel++)
// {
// currentBlueTotal += (CGFloat)imageData[(currentPixel * 4)] / 255.0f;
// currentGreenTotal += (CGFloat)imageData[(currentPixel * 4) + 1] / 255.0f;
// currentRedTotal += (CGFloat)imageData[(currentPixel * 4 + 2)] / 255.0f;
// currentAlphaTotal += (CGFloat)imageData[(currentPixel * 4) + 3] / 255.0f;
// }
//
// NSLog(@"Debug, average input image red: %f, green: %f, blue: %f, alpha: %f", currentRedTotal / (CGFloat)totalNumberOfPixels, currentGreenTotal / (CGFloat)totalNumberOfPixels, currentBlueTotal / (CGFloat)totalNumberOfPixels, currentAlphaTotal / (CGFloat)totalNumberOfPixels);
runSynchronouslyOnVideoProcessingQueue(^{
[GPUImageContext useImageProcessingContext];
outputFramebuffer = [[GPUImageContext sharedFramebufferCache] fetchFramebufferForSize:pixelSizeToUseForTexture onlyTexture:YES];
[outputFramebuffer disableReferenceCounting];
glBindTexture(GL_TEXTURE_2D, [outputFramebuffer texture]);
if (self.shouldSmoothlyScaleOutput)
{
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);
}
// no need to use self.outputTextureOptions here since pictures need this texture formats and type
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, (int)pixelSizeToUseForTexture.width, (int)pixelSizeToUseForTexture.height, 0, format, GL_UNSIGNED_BYTE, imageData);
//是否生成mipmaps
if (self.shouldSmoothlyScaleOutput)
{
glGenerateMipmap(GL_TEXTURE_2D);
}
glBindTexture(GL_TEXTURE_2D, 0);
});
//7最后释放资源
if (shouldRedrawUsingCoreGraphics)
{
free(imageData);
}
else
{
if (dataFromImageDataProvider)
{
CFRelease(dataFromImageDataProvider);
}
}
return self;
}
  • 其它方法。这些方法主要是与图片处理相关。

// 处理图片
- (void)processImage;
{
[self processImageWithCompletionHandler:nil];
}
// 处理图片,可以传入处理完回调的block
- (BOOL)processImageWithCompletionHandler:(void (^)(void))completion;
{
hasProcessedImage = YES;
// dispatch_semaphore_wait(imageUpdateSemaphore, DISPATCH_TIME_FOREVER);
if (dispatch_semaphore_wait(imageUpdateSemaphore, DISPATCH_TIME_NOW) != 0)
{
return NO;
}
runAsynchronouslyOnVideoProcessingQueue(^{
for (id<GPUImageInput> currentTarget in targets)
{
NSInteger indexOfObject = [targets indexOfObject:currentTarget];
NSInteger textureIndexOfTarget = [[targetTextureIndices objectAtIndex:indexOfObject] integerValue];
[currentTarget setCurrentlyReceivingMonochromeInput:NO];
[currentTarget setInputSize:pixelSizeOfImage atIndex:textureIndexOfTarget];
[currentTarget setInputFramebuffer:outputFramebuffer atIndex:textureIndexOfTarget];
[currentTarget newFrameReadyAtTime:kCMTimeIndefinite atIndex:textureIndexOfTarget];
}
dispatch_semaphore_signal(imageUpdateSemaphore);
if (completion != nil) {
completion();
}
});
return YES;
}
- (void)processImageUpToFilter:(GPUImageOutput<GPUImageInput> *)finalFilterInChain withCompletionHandler:(void (^)(UIImage *processedImage))block;
{
[finalFilterInChain useNextFrameForImageCapture];
[self processImageWithCompletionHandler:^{
UIImage *imageFromFilter = [finalFilterInChain imageFromCurrentFramebuffer];
//返回处理后的图片
block(imageFromFilter);
}];
}
// 输出图片大小,由于图像大小可能被调整(详见初始化方法)。因此,提供了获取图像大小的方法。
- (CGSize)outputImageSize;
{
return pixelSizeOfImage;
}
// 由响应链的final filter生成UIImage图像
- (void)addTarget:(id<GPUImageInput>)newTarget atTextureLocation:(NSInteger)textureLocation;
{
[super addTarget:newTarget atTextureLocation:textureLocation];
if (hasProcessedImage)
{
[newTarget setInputSize:pixelSizeOfImage atIndex:textureLocation];
[newTarget newFrameReadyAtTime:kCMTimeIndefinite atIndex:textureLocation];
}
}