CVPixelBufferRef与UIImage的互相转换
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CVPixelBufferRef与UIImage的互相转换
//// ViewController.m// test_image_covert_data_01//// Created by jeffasd on 2016/9/30.// Copyright © 2016年 jeffasd. All rights reserved.//#import "ViewController.h"#define RETAINED_BUFFER_COUNT 4@interface ViewController ()@property (nonatomic, assign) CVPixelBufferPoolRef pixelBufferPool;@end@implementation ViewController#pragma CVPixelBufferRef与UIImage的互相转换- (void)viewDidLoad { [super viewDidLoad]; self.pixelBufferPool = NULL; UIImage *image = [UIImage imageNamed:@"atlastest"]; CVPixelBufferRef pixelBuffer = [self CVPixelBufferRefFromUiImage:image]; //CVPixelBufferRef pixelBuffer = [self pixelBufferFasterFromImage:image]; //CVPixelBufferRef pixelBuffer = [[self class] pixelBufferFromCGImage:image.CGImage]; //UIImage *covertImage = [[self class] imageFromCVPixelBufferRef0:pixelBuffer]; //UIImage *covertImage = [[self class] imageFromCVPixelBufferRef1:pixelBuffer]; //UIImage *covertImage = [[self class] imageFromCVPixelBufferRef2:pixelBuffer];// covertImage = nil;// UIImage *decodeImage = [[self class] decodeImageWithImage:image]; decodeImage = nil; CVPixelBufferRef pixelBuffer1 = [self pixelBufferFromImageWithPool:NULL image:image]; pixelBuffer1 = nil; //covertImage = nil;}static OSType inputPixelFormat(){ //注意CVPixelBufferCreate函数不支持 kCVPixelFormatType_32RGBA 等格式 不知道为什么。 //支持kCVPixelFormatType_32ARGB和kCVPixelFormatType_32BGRA等 iPhone为小端对齐因此kCVPixelFormatType_32ARGB和kCVPixelFormatType_32BGRA都需要和kCGBitmapByteOrder32Little配合使用 //注意当inputPixelFormat为kCVPixelFormatType_32BGRA时bitmapInfo不能是kCGImageAlphaNone，kCGImageAlphaLast，kCGImageAlphaFirst，kCGImageAlphaOnly。 //注意iPhone的大小端对齐方式为小段对齐 可以使用宏 kCGBitmapByteOrder32Host 来解决大小端对齐 大小端对齐必须设置为kCGBitmapByteOrder32Little。 //return kCVPixelFormatType_32RGBA;//iPhone不支持此输入格式!!! return kCVPixelFormatType_32BGRA; //return kCVPixelFormatType_32ARGB;}static uint32_t bitmapInfoWithPixelFormatType(OSType inputPixelFormat){ /* CGBitmapInfo的设置 uint32_t bitmapInfo = CGImageAlphaInfo | CGBitmapInfo; 当inputPixelFormat=kCVPixelFormatType_32BGRA CGBitmapInfo的正确的设置 只有如下两种正确设置 uint32_t bitmapInfo = kCGImageAlphaPremultipliedFirst | kCGBitmapByteOrder32Host; uint32_t bitmapInfo = kCGImageAlphaNoneSkipFirst | kCGBitmapByteOrder32Host; typedef CF_ENUM(uint32_t, CGImageAlphaInfo) { kCGImageAlphaNone, For example, RGB. kCGImageAlphaPremultipliedLast, For example, premultiplied RGBA kCGImageAlphaPremultipliedFirst, For example, premultiplied ARGB kCGImageAlphaLast, For example, non-premultiplied RGBA kCGImageAlphaFirst, For example, non-premultiplied ARGB kCGImageAlphaNoneSkipLast, For example, RBGX. kCGImageAlphaNoneSkipFirst, For example, XRGB. kCGImageAlphaOnly No color data, alpha data only }; 当inputPixelFormat=kCVPixelFormatType_32ARGB CGBitmapInfo的正确的设置 只有如下两种正确设置 uint32_t bitmapInfo = kCGImageAlphaPremultipliedFirst | kCGBitmapByteOrder32Big; uint32_t bitmapInfo = kCGImageAlphaNoneSkipFirst | kCGBitmapByteOrder32Big; */ if (inputPixelFormat == kCVPixelFormatType_32BGRA) { //uint32_t bitmapInfo = kCGImageAlphaPremultipliedFirst | kCGBitmapByteOrder32Host; //此格式也可以 uint32_t bitmapInfo = kCGImageAlphaNoneSkipFirst | kCGBitmapByteOrder32Host; return bitmapInfo; }else if (inputPixelFormat == kCVPixelFormatType_32ARGB){ uint32_t bitmapInfo = kCGImageAlphaPremultipliedFirst | kCGBitmapByteOrder32Big; //此格式也可以 //uint32_t bitmapInfo = kCGImageAlphaNoneSkipFirst | kCGBitmapByteOrder32Big; return bitmapInfo; }else{ NSLog(@"不支持此格式"); return 0; }}static CVPixelBufferPoolRef createPixelBufferPoolInner( int32_t width, int32_t height, OSType pixelFormat, int32_t maxBufferCount ){ CVPixelBufferPoolRef outputPool = NULL; NSDictionary *sourcePixelBufferOptions = @{ (id)kCVPixelBufferPixelFormatTypeKey : @(pixelFormat), (id)kCVPixelBufferWidthKey : @(width), (id)kCVPixelBufferHeightKey : @(height), //(id)kCVPixelFormatOpenGLESCompatibility : @(YES), (id)kCVPixelBufferIOSurfacePropertiesKey : @{ /*empty dictionary*/ } }; NSDictionary *pixelBufferPoolOptions = @{ (id)kCVPixelBufferPoolMinimumBufferCountKey : @(maxBufferCount) }; CVPixelBufferPoolCreate( kCFAllocatorDefault, (__bridge CFDictionaryRef)pixelBufferPoolOptions, (__bridge CFDictionaryRef)sourcePixelBufferOptions, &outputPool ); return outputPool;}static CVPixelBufferPoolRef createCVPixelBufferPoolRef(int32_t imageWidth, int32_t imageHeight){ OSType pixelFormat = inputPixelFormat(); int32_t maxRetainedBufferCount = RETAINED_BUFFER_COUNT; CVPixelBufferPoolRef bufferPool = createPixelBufferPoolInner( imageWidth, imageHeight, pixelFormat, maxRetainedBufferCount ); if ( ! bufferPool ) { NSLog( @"Problem initializing a buffer pool." ); } NSLog( @"success initializing a buffer pool." ); return bufferPool;}- (CVPixelBufferRef)pixelBufferFromImageWithPool:(CVPixelBufferPoolRef)pixelBufferPool image:(UIImage *)image{ CVPixelBufferRef pxbuffer = NULL; NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys: [NSNumber numberWithBool:YES], kCVPixelBufferCGImageCompatibilityKey, [NSNumber numberWithBool:YES], kCVPixelBufferCGBitmapContextCompatibilityKey, nil]; size_t width = CGImageGetWidth(image.CGImage); size_t height = CGImageGetHeight(image.CGImage); size_t bytesPerRow = CGImageGetBytesPerRow(image.CGImage);#if 0 CGBitmapInfo bitmapInfo = CGImageGetBitmapInfo(image.CGImage);#endif void *pxdata = NULL; if (pixelBufferPool == NULL){ NSLog(@"pixelBufferPool is null!"); CVPixelBufferPoolRef bufferPool = createCVPixelBufferPoolRef((int32_t)width, (int32_t)height); self.pixelBufferPool = bufferPool; pixelBufferPool = bufferPool; } CVReturn status = CVPixelBufferPoolCreatePixelBuffer (NULL, pixelBufferPool, &pxbuffer); if (pxbuffer == NULL) { status = CVPixelBufferCreate(kCFAllocatorDefault, width, height, inputPixelFormat(), (__bridge CFDictionaryRef) options, &pxbuffer); } NSParameterAssert(status == kCVReturnSuccess && pxbuffer != NULL); CVPixelBufferLockBaseAddress(pxbuffer, 0); pxdata = CVPixelBufferGetBaseAddress(pxbuffer); NSParameterAssert(pxdata != NULL); #if 1 - 此去掉alpha通道效率更高 CGColorSpaceRef rgbColorSpace = CGColorSpaceCreateDeviceRGB(); CGBitmapInfo bitmapInfo = kCGBitmapByteOrder32Host; //对于生成CVPixelBufferRef无法使用此方法但是对于解码图片可以使用此方法// CGImageAlphaInfo alphaInfo = CGImageGetAlphaInfo(image.CGImage);// if (alphaInfo == kCGImageAlphaNone || alphaInfo == kCGImageAlphaOnly) {// alphaInfo = kCGImageAlphaNoneSkipFirst;// } else if (alphaInfo == kCGImageAlphaFirst) {// alphaInfo = kCGImageAlphaPremultipliedFirst;// } else if (alphaInfo == kCGImageAlphaLast) {// alphaInfo = kCGImageAlphaPremultipliedLast;// }// bitmapInfo |= alphaInfo; bitmapInfo = bitmapInfoWithPixelFormatType(inputPixelFormat()); size_t bitsPerComponent = CGImageGetBitsPerComponent(image.CGImage); CGContextRef context = CGBitmapContextCreate(pxdata, width, height,bitsPerComponent,bytesPerRow, rgbColorSpace, bitmapInfo); NSParameterAssert(context); CGContextConcatCTM(context, CGAffineTransformMakeRotation(0)); CGContextDrawImage(context, CGRectMake(0, 0, width,height), image.CGImage); CGColorSpaceRelease(rgbColorSpace); CGContextRelease(context);#else //- 此方法获取的图片可能无法还原真实的图片 CFDataRef dataFromImageDataProvider = CGDataProviderCopyData(CGImageGetDataProvider(image.CGImage)); GLubyte *imageData = (GLubyte *)CFDataGetBytePtr(dataFromImageDataProvider); #if 0 CFIndex length = CFDataGetLength(dataFromImageDataProvider); memcpy(pxdata,imageData,length); #else CVPixelBufferCreateWithBytes(kCFAllocatorDefault,width,height,inputPixelFormat(),imageData,bytesPerRow,NULL,NULL,(__bridge CFDictionaryRef)options,&pxbuffer); #endif CFRelease(dataFromImageDataProvider);#endif return pxbuffer;}/** UIImage covert to CVPixelBufferRef *///方法1 此方法能还原真实的图片- (CVPixelBufferRef)CVPixelBufferRefFromUiImage:(UIImage *)img { CGSize size = img.size; CGImageRef image = [img CGImage]; NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys: [NSNumber numberWithBool:YES], kCVPixelBufferCGImageCompatibilityKey, [NSNumber numberWithBool:YES], kCVPixelBufferCGBitmapContextCompatibilityKey, nil]; CVPixelBufferRef pxbuffer = NULL; CVReturn status = CVPixelBufferCreate(kCFAllocatorDefault, size.width, size.height, inputPixelFormat(), (__bridge CFDictionaryRef) options, &pxbuffer); NSParameterAssert(status == kCVReturnSuccess && pxbuffer != NULL); CVPixelBufferLockBaseAddress(pxbuffer, 0); void *pxdata = CVPixelBufferGetBaseAddress(pxbuffer); NSParameterAssert(pxdata != NULL); CGColorSpaceRef rgbColorSpace = CGColorSpaceCreateDeviceRGB(); //CGBitmapInfo的设置 //uint32_t bitmapInfo = CGImageAlphaInfo | CGBitmapInfo; //当inputPixelFormat=kCVPixelFormatType_32BGRA CGBitmapInfo的正确的设置 //uint32_t bitmapInfo = kCGImageAlphaPremultipliedFirst | kCGBitmapByteOrder32Host; //uint32_t bitmapInfo = kCGImageAlphaNoneSkipFirst | kCGBitmapByteOrder32Host; //当inputPixelFormat=kCVPixelFormatType_32ARGB CGBitmapInfo的正确的设置 //uint32_t bitmapInfo = kCGImageAlphaPremultipliedFirst | kCGBitmapByteOrder32Big; //uint32_t bitmapInfo = kCGImageAlphaNoneSkipFirst | kCGBitmapByteOrder32Big; uint32_t bitmapInfo = bitmapInfoWithPixelFormatType(inputPixelFormat()); CGContextRef context = CGBitmapContextCreate(pxdata, size.width, size.height, 8, 4*size.width, rgbColorSpace, bitmapInfo); NSParameterAssert(context); CGContextDrawImage(context, CGRectMake(0, 0, CGImageGetWidth(image), CGImageGetHeight(image)), image); CVPixelBufferUnlockBaseAddress(pxbuffer, 0); CGColorSpaceRelease(rgbColorSpace); CGContextRelease(context); return pxbuffer;}/** UIImage covert to CVPixelBufferRef *///方法2 注意此方法在处理某些图片时可能无法还原真实的图片- (CVPixelBufferRef)pixelBufferFasterFromImage:(UIImage *)image{ CVPixelBufferRef pxbuffer = NULL; NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys: [NSNumber numberWithBool:YES], kCVPixelBufferCGImageCompatibilityKey, [NSNumber numberWithBool:YES], kCVPixelBufferCGBitmapContextCompatibilityKey, nil]; size_t width = CGImageGetWidth(image.CGImage); size_t height = CGImageGetHeight(image.CGImage); size_t bytesPerRow = CGImageGetBytesPerRow(image.CGImage); CFDataRef dataFromImageDataProvider = CGDataProviderCopyData(CGImageGetDataProvider(image.CGImage)); GLubyte *imageData = (GLubyte *)CFDataGetBytePtr(dataFromImageDataProvider); //kCGImageAlphaNoneSkipLast, /* For example, RBGX. */ CGColorSpaceRef colorspace = CGImageGetColorSpace(image.CGImage); CGImageAlphaInfo alphainfo = CGImageGetAlphaInfo(image.CGImage); CGBitmapInfo bitmapInfo = CGImageGetBitmapInfo(image.CGImage); const CGFloat *decode = CGImageGetDecode(image.CGImage); NSString *str = CGImageGetUTType(image.CGImage); // kCVPixelFormatType_32ARGB = 0x00000020, /* 32 bit ARGB */// kCVPixelFormatType_32BGRA = 'BGRA', /* 32 bit BGRA */// kCVPixelFormatType_32ABGR = 'ABGR', /* 32 bit ABGR */不能使用// kCVPixelFormatType_32RGBA = 'RGBA', /* 32 bit RGBA */不能使用 //CVPixelBufferCreateWithBytes这里是很耗时的，要重新创建。 //此方法获取的CVPixelBufferRef不一定正确 如原始图片的CGImageAlphaInfo为kCGImageAlphaNoneSkipLast由于pixelFormatType没有RBGX类型的格式就没法还原原始的图片。 CVPixelBufferCreateWithBytes(kCFAllocatorDefault,width,height,kCVPixelFormatType_32BGRA,imageData,bytesPerRow,NULL,NULL,(__bridge CFDictionaryRef)options,&pxbuffer); CFRelease(dataFromImageDataProvider); CVPixelBufferRetain(pxbuffer); return pxbuffer;}+ (CVPixelBufferRef) pixelBufferFromCGImage: (CGImageRef) image{ CGSize frameSize = CGSizeMake(CGImageGetWidth(image), CGImageGetHeight(image)); NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys: [NSNumber numberWithBool:NO], kCVPixelBufferCGImageCompatibilityKey, [NSNumber numberWithBool:NO], kCVPixelBufferCGBitmapContextCompatibilityKey, nil]; CVPixelBufferRef pxbuffer = NULL; CVReturn status = CVPixelBufferCreate(kCFAllocatorDefault, frameSize.width, frameSize.height, kCVPixelFormatType_32BGRA, (__bridge CFDictionaryRef) options, &pxbuffer); NSParameterAssert(status == kCVReturnSuccess && pxbuffer != NULL); CVPixelBufferLockBaseAddress(pxbuffer, 0); void *pxdata = CVPixelBufferGetBaseAddress(pxbuffer); CGColorSpaceRef rgbColorSpace = CGColorSpaceCreateDeviceRGB(); CGContextRef context = CGBitmapContextCreate(pxdata, frameSize.width, frameSize.height, 8, 4*frameSize.width, rgbColorSpace, kCGBitmapByteOrder32Little | kCGImageAlphaNoneSkipFirst); CGContextDrawImage(context, CGRectMake(0, 0, CGImageGetWidth(image), CGImageGetHeight(image)), image);//这个站CPU 相当高 CGColorSpaceRelease(rgbColorSpace); CGContextRelease(context); CVPixelBufferUnlockBaseAddress(pxbuffer, 0); return pxbuffer;}//CVPixelBufferRef 是 CMSampleBufferRef 解码后的数据/** UIImage covert to CMSampleBufferRef *//** CVPixelBufferRef covert to UIImage */+ (UIImage *)imageFromCVPixelBufferRef0:(CVPixelBufferRef)pixelBuffer{ // MUST READ-WRITE LOCK THE PIXEL BUFFER!!!! CVPixelBufferLockBaseAddress(pixelBuffer, 0); CIImage *ciImage = [CIImage imageWithCVPixelBuffer:pixelBuffer]; CVPixelBufferUnlockBaseAddress(pixelBuffer, 0); CIContext *temporaryContext = [CIContext contextWithOptions:nil]; CGImageRef videoImage = [temporaryContext createCGImage:ciImage fromRect:CGRectMake(0, 0, CVPixelBufferGetWidth(pixelBuffer), CVPixelBufferGetHeight(pixelBuffer))]; UIImage *uiImage = [UIImage imageWithCGImage:videoImage]; CGImageRelease(videoImage); CVPixelBufferRelease(pixelBuffer); return uiImage;}static OSStatus CreateCGImageFromCVPixelBuffer(CVPixelBufferRef pixelBuffer, CGImageRef *imageOut){ OSStatus err = noErr; OSType sourcePixelFormat; size_t width, height, sourceRowBytes; void *sourceBaseAddr = NULL; CGBitmapInfo bitmapInfo; CGColorSpaceRef colorspace = NULL; CGDataProviderRef provider = NULL; CGImageRef image = NULL; sourcePixelFormat = CVPixelBufferGetPixelFormatType( pixelBuffer ); if ( kCVPixelFormatType_32ARGB == sourcePixelFormat ) bitmapInfo = kCGBitmapByteOrder32Big | kCGImageAlphaNoneSkipFirst; else if ( kCVPixelFormatType_32BGRA == sourcePixelFormat ) bitmapInfo = kCGBitmapByteOrder32Little | kCGImageAlphaNoneSkipFirst; else return -95014; // only uncompressed pixel formats sourceRowBytes = CVPixelBufferGetBytesPerRow( pixelBuffer ); width = CVPixelBufferGetWidth( pixelBuffer ); height = CVPixelBufferGetHeight( pixelBuffer ); CVPixelBufferLockBaseAddress( pixelBuffer, 0 ); sourceBaseAddr = CVPixelBufferGetBaseAddress( pixelBuffer ); colorspace = CGColorSpaceCreateDeviceRGB(); CVPixelBufferRetain( pixelBuffer ); provider = CGDataProviderCreateWithData( (void *)pixelBuffer, sourceBaseAddr, sourceRowBytes * height, ReleaseCVPixelBuffer); image = CGImageCreate(width, height, 8, 32, sourceRowBytes, colorspace, bitmapInfo, provider, NULL, true, kCGRenderingIntentDefault); if ( err && image ) { CGImageRelease( image ); image = NULL; } if ( provider ) CGDataProviderRelease( provider ); if ( colorspace ) CGColorSpaceRelease( colorspace ); *imageOut = image; return err;}static void ReleaseCVPixelBuffer(void *pixel, const void *data, size_t size){ CVPixelBufferRef pixelBuffer = (CVPixelBufferRef)pixel; CVPixelBufferUnlockBaseAddress( pixelBuffer, 0 ); CVPixelBufferRelease( pixelBuffer );}+(UIImage *)imageFromCVPixelBufferRef1:(CVPixelBufferRef)pixelBuffer{ UIImage *image; @autoreleasepool { CGImageRef cgImage = NULL; CVPixelBufferRef pb = (CVPixelBufferRef)pixelBuffer; CVPixelBufferLockBaseAddress(pb, kCVPixelBufferLock_ReadOnly); OSStatus res = CreateCGImageFromCVPixelBuffer(pb,&cgImage); if (res == noErr){ image= [UIImage imageWithCGImage:cgImage scale:1.0 orientation:UIImageOrientationUp]; } CVPixelBufferUnlockBaseAddress(pb, kCVPixelBufferLock_ReadOnly); CGImageRelease(cgImage); } return image;}//第二种+(UIImage *)imageFromCVPixelBufferRef2:(CVPixelBufferRef)pixelBuffer{ CVPixelBufferRef pb = (CVPixelBufferRef)pixelBuffer; CVPixelBufferLockBaseAddress(pb, kCVPixelBufferLock_ReadOnly); int w = CVPixelBufferGetWidth(pb); int h = CVPixelBufferGetHeight(pb); int r = CVPixelBufferGetBytesPerRow(pb); int bytesPerPixel = r/w; unsigned char *buffer = CVPixelBufferGetBaseAddress(pb); UIGraphicsBeginImageContext(CGSizeMake(w, h)); CGContextRef c = UIGraphicsGetCurrentContext(); unsigned char *data = CGBitmapContextGetData(c); if (data != NULL) { int maxY = h; for(int y = 0; y<maxY; y++) { for(int x = 0; x<w; x++) { int offset = bytesPerPixel*((w*y)+x); data[offset] = buffer[offset]; // R data[offset+1] = buffer[offset+1]; // G data[offset+2] = buffer[offset+2]; // B data[offset+3] = buffer[offset+3]; // A } } } UIImage *img = UIGraphicsGetImageFromCurrentImageContext(); UIGraphicsEndImageContext(); CVPixelBufferUnlockBaseAddress(pb, kCVPixelBufferLock_ReadOnly); return img;}/** CMSampleBufferRef covert to UIImage *//** CMSampleBufferRef covert to CVPixelBufferRef *//** decode compress image to bitmap iamge */+ (UIImage *)decodeImageWithImage:(UIImage *)imageToPredraw{ // Always use a device RGB color space for simplicity and predictability what will be going on. CGColorSpaceRef colorSpaceDeviceRGBRef = CGColorSpaceCreateDeviceRGB(); // Early return on failure! if (!colorSpaceDeviceRGBRef) { NSLog(@"Failed to `CGColorSpaceCreateDeviceRGB` for image %@", imageToPredraw); return imageToPredraw; } // "In iOS 4.0 and later, and OS X v10.6 and later, you can pass NULL if you want Quartz to allocate memory for the bitmap." (source: docs) void *data = NULL; size_t width = imageToPredraw.size.width; size_t height = imageToPredraw.size.height; size_t bitsPerComponent = CHAR_BIT;//一个像素的单个组成部分的位数 如RGBA 此值指定R,G,B,A,每个分量占的位数为8bit。 #if 1 // Even when the image doesn't have transparency, we have to add the extra channel because Quartz doesn't support other pixel formats than 32 bpp/8 bpc for RGB: // kCGImageAlphaNoneSkipFirst, kCGImageAlphaNoneSkipLast, kCGImageAlphaPremultipliedFirst, kCGImageAlphaPremultipliedLast // (source: docs "Quartz 2D Programming Guide > Graphics Contexts > Table 2-1 Pixel formats supported for bitmap graphics contexts") size_t numberOfComponents = CGColorSpaceGetNumberOfComponents(colorSpaceDeviceRGBRef) + 1; // 4: RGB + A size_t bitsPerPixel = (bitsPerComponent * numberOfComponents);//一个像素点占用的位数 如RGBA=8*4 size_t bytesPerPixel = (bitsPerPixel / BYTE_SIZE);//一个像素点占用的字节数 size_t bytesPerRow = (bytesPerPixel * width);//一行的全部像素占用的字节数#else size_t bytesPerRow = 0;//对于CGBitmapContextCreate函数当bytesPerRow=0系统不仅会为我们自动计算，而且还会进行 cache line alignment 的优化#endif CGBitmapInfo bitmapInfo = kCGBitmapByteOrder32Host; CGImageAlphaInfo alphaInfo = CGImageGetAlphaInfo(imageToPredraw.CGImage); // If the alpha info doesn't match to one of the supported formats (see above), pick a reasonable supported one. // "For bitmaps created in iOS 3.2 and later, the drawing environment uses the premultiplied ARGB format to store the bitmap data." (source: docs) if (alphaInfo == kCGImageAlphaNone || alphaInfo == kCGImageAlphaOnly) { alphaInfo = kCGImageAlphaNoneSkipFirst; } else if (alphaInfo == kCGImageAlphaFirst) { alphaInfo = kCGImageAlphaPremultipliedFirst; } else if (alphaInfo == kCGImageAlphaLast) { alphaInfo = kCGImageAlphaPremultipliedLast; } // "The constants for specifying the alpha channel information are declared with the `CGImageAlphaInfo` type but can be passed to this parameter safely." (source: docs) bitmapInfo |= alphaInfo; // Create our own graphics context to draw to; `UIGraphicsGetCurrentContext`/`UIGraphicsBeginImageContextWithOptions` doesn't create a new context but returns the current one which isn't thread-safe (e.g. main thread could use it at the same time). // Note: It's not worth caching the bitmap context for multiple frames ("unique key" would be `width`, `height` and `hasAlpha`), it's ~50% slower. Time spent in libRIP's `CGSBlendBGRA8888toARGB8888` suddenly shoots up -- not sure why. //data为NULL系统自动分配内存空间 CGContextRef bitmapContextRef = CGBitmapContextCreate(data, width, height, bitsPerComponent, bytesPerRow, colorSpaceDeviceRGBRef, bitmapInfo); CGColorSpaceRelease(colorSpaceDeviceRGBRef); // Early return on failure! if (!bitmapContextRef) { NSLog(@"Failed to `CGBitmapContextCreate` with color space %@ and parameters (width: %zu height: %zu bitsPerComponent: %zu bytesPerRow: %zu) for image %@", colorSpaceDeviceRGBRef, width, height, bitsPerComponent, bytesPerRow, imageToPredraw); return imageToPredraw; } // Draw image in bitmap context and create image by preserving receiver's properties. CGContextDrawImage(bitmapContextRef, CGRectMake(0.0, 0.0, imageToPredraw.size.width, imageToPredraw.size.height), imageToPredraw.CGImage); CGImageRef predrawnImageRef = CGBitmapContextCreateImage(bitmapContextRef); UIImage *predrawnImage = [UIImage imageWithCGImage:predrawnImageRef scale:imageToPredraw.scale orientation:imageToPredraw.imageOrientation]; CGImageRelease(predrawnImageRef); CGContextRelease(bitmapContextRef); // Early return on failure! if (!predrawnImage) { NSLog(@"Failed to `imageWithCGImage:scale:orientation:` with image ref %@ created with color space %@ and bitmap context %@ and properties and properties (scale: %f orientation: %ld) for image %@", predrawnImageRef, colorSpaceDeviceRGBRef, bitmapContextRef, imageToPredraw.scale, (long)imageToPredraw.imageOrientation, imageToPredraw); return imageToPredraw; } return predrawnImage;}- (void)didReceiveMemoryWarning { [super didReceiveMemoryWarning]; // Dispose of any resources that can be recreated.}@end阅读全文
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