在iOS多媒体开发时，需要经常转换图像格式以便调试。下面列了一些常用工具方法，在UIImage, CVPixelBufferRef,Texture之间完成格式转换。

1. 其他格式转为UIImage

1.1 CVImageBufferRef (RGB)转为UIImage

- (UIImage *)imageFromRGBImageBuffer:(CVImageBufferRef)imageBuffer {
    CVPixelBufferLockBaseAddress(imageBuffer, 0);
    void *baseAddress = CVPixelBufferGetBaseAddress(imageBuffer);
    size_t bytesPerRow = CVPixelBufferGetBytesPerRow(imageBuffer);
    size_t width = CVPixelBufferGetWidth(imageBuffer);
    size_t height = CVPixelBufferGetHeight(imageBuffer);
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    CGContextRef context = CGBitmapContextCreate(baseAddress, width, height, 8,bytesPerRow, colorSpace, kCGBitmapByteOrder32Little | kCGImageAlphaPremultipliedFirst);
    CGImageRef quartzImage = CGBitmapContextCreateImage(context);
    CVPixelBufferUnlockBaseAddress(imageBuffer,0);
    CGContextRelease(context);
    CGColorSpaceRelease(colorSpace);
    UIImage *image = [UIImage imageWithCGImage:quartzImage];
    CGImageRelease(quartzImage);
    return (image);
}

1.2 CVImageBufferRef (YUV)转为UIImage

- (UIImage *)imageFromYUVImageBuffer:(CVImageBufferRef)imageBuffer {
    CVPixelBufferLockBaseAddress(imageBuffer, 0);
    size_t bytesPerRow = CVPixelBufferGetBytesPerRowOfPlane(imageBuffer, 0);
    size_t width = CVPixelBufferGetWidthOfPlane(imageBuffer, 0);
    size_t height = CVPixelBufferGetHeightOfPlane(imageBuffer, 0);
    void *lumaAddress = CVPixelBufferGetBaseAddress(imageBuffer);
    CGColorSpaceRef rgbSpace = CGColorSpaceCreateDeviceGray();
    CGContextRef context = CGBitmapContextCreate(lumaAddress, width, height, 8, bytesPerRow, rgbSpace, kCGBitmapByteOrderDefault );
    CGImageRef imageRef = CGBitmapContextCreateImage(context);
    CGContextRelease(context);
    CVPixelBufferUnlockBaseAddress(imageBuffer, 0);
    UIImage *image = [UIImage imageWithCGImage:imageRef];
    CGImageRelease(imageRef);
    return image;
}

1.3 纹理 (Texture)转为UIImage

- (UIImage *)imageFromTextureWithwidth:(int)width height:(int)height {
    // glActiveTexture(GL_TEXTURE1); 先绑定某个纹理
    int size = width * height * 4;
    GLubyte *buffer = malloc(size);
    glReadPixels(0, 0, width, height, GL_RGBA, GL_UNSIGNED_BYTE, buffer);
    CGDataProviderRef provider = CGDataProviderCreateWithData(NULL, buffer, size, NULL);
    int bitsPerComponent = 8;
    int bitsPerPixel = 32;
    int bytesPerRow = 4 * width;
    CGColorSpaceRef colorSpaceRef = CGColorSpaceCreateDeviceRGB();
    CGBitmapInfo bitmapInfo = kCGBitmapByteOrderDefault;
    CGColorRenderingIntent renderingIntent = kCGRenderingIntentDefault;
    CGImageRef imageRef = CGImageCreate(width, height, bitsPerComponent, bitsPerPixel, bytesPerRow, colorSpaceRef, bitmapInfo, provider, NULL, NO, renderingIntent);
    UIImage *image = [UIImage imageWithCGImage:imageRef];
    free(buffer);
    return image;
}

1.4 data (RGB)转为UIImage

- (UIImage *)imageFromRGBData:(void *)data width:(int)width height:(int)height {
    CGColorSpaceRef rgbSpace = CGColorSpaceCreateDeviceRGB();
    CGContextRef context = CGBitmapContextCreate(data, width, height, 8, width*4, rgbSpace, kCGImageAlphaPremultipliedFirst | kCGBitmapByteOrder32Little );
    CGImageRef imageRef = CGBitmapContextCreateImage(context);
    CGContextRelease(context);
    UIImage *image = [UIImage imageWithCGImage:imageRef];
    CGImageRelease(imageRef);
    return image;
}

1.5 data (Y)转为UIImage

- (UIImage *)imageFromYData:(void *)data width:(int)width height:(int)height {
    CGColorSpaceRef rgbSpace = CGColorSpaceCreateDeviceGray();
    CGContextRef context = CGBitmapContextCreate(data, width, height, 8, width, rgbSpace, kCGBitmapByteOrderDefault );
    CGImageRef imageRef = CGBitmapContextCreateImage(context);
    CGContextRelease(context);
    UIImage *image = [UIImage imageWithCGImage:imageRef];
    CGImageRelease(imageRef);
    return image;
}

2. UIImage转为其他格式

2.1 UIImage转为CVPixelBufferRef(RGB)

- (CVPixelBufferRef)imageToRGBPixelBuffer:(UIImage *)image {
    CGSize frameSize = CGSizeMake(CGImageGetWidth(image.CGImage),CGImageGetHeight(image.CGImage));
    NSDictionary *options =
    [NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithBool:YES],kCVPixelBufferCGImageCompatibilityKey,[NSNumber numberWithBool:YES],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, CVPixelBufferGetBytesPerRow(pxbuffer),rgbColorSpace,(CGBitmapInfo)kCGBitmapByteOrder32Little | kCGImageAlphaPremultipliedFirst);
    CGContextDrawImage(context, CGRectMake(0, 0, CGImageGetWidth(image.CGImage),CGImageGetHeight(image.CGImage)), image.CGImage);
    CGColorSpaceRelease(rgbColorSpace);
    CGContextRelease(context);
    CVPixelBufferUnlockBaseAddress(pxbuffer, 0);
    return pxbuffer;
}

2.2 UIImage转为CVPixelBufferRef(YUV)

- (CVPixelBufferRef)imageToYUVPixelBuffer:(UIImage *)image {
    CGSize frameSize = CGSizeMake(CGImageGetWidth(image.CGImage), CGImageGetHeight(image.CGImage));
    NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys:
                             [NSNumber numberWithBool:YES],kCVPixelBufferCGImageCompatibilityKey,
                             [NSNumber numberWithBool:YES],kCVPixelBufferCGBitmapContextCompatibilityKey,nil];
    CVPixelBufferRef pxbuffer = NULL;
    CVPixelBufferCreate(kCFAllocatorDefault, frameSize.width, frameSize.height,kCVPixelFormatType_420YpCbCr8BiPlanarFullRange, (__bridge CFDictionaryRef)options,&pxbuffer);
    CVPixelBufferLockBaseAddress(pxbuffer, 0);
    void *pxdata = CVPixelBufferGetBaseAddressOfPlane(pxbuffer,0);
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceGray();
    CGContextRef context = CGBitmapContextCreate(pxdata, frameSize.width, frameSize.height,8,CVPixelBufferGetBytesPerRowOfPlane(pxbuffer, 0),colorSpace,kCGImageAlphaNone);
    CGContextDrawImage(context, CGRectMake(0, 0, CGImageGetWidth(image.CGImage),CGImageGetHeight(image.CGImage)), image.CGImage);
    CGColorSpaceRelease(colorSpace);
    CGContextRelease(context);
    CVPixelBufferUnlockBaseAddress(pxbuffer, 0);
    return pxbuffer;
}