iOS-删除图片透明通道，并将rgb图片转换为bgr图片

可以根据自己的需求修改代码，不需要转bgr的可以注释掉转换部分

• OC代码

+ (NSData *)getBGRWithImage:(UIImage *)image
{
    int RGBA = 4;
    int RGB  = 3;
    
    CGImageRef imageRef = [image CGImage];
    
    size_t width = CGImageGetWidth(imageRef);
    size_t height = CGImageGetHeight(imageRef);
    
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    unsigned char *rawData = (unsigned char *) malloc(width * height * sizeof(unsigned char) * RGBA);
    NSUInteger bytesPerPixel = RGBA;
    NSUInteger bytesPerRow = bytesPerPixel * width;
    NSUInteger bitsPerComponent = 8;
    CGContextRef context = CGBitmapContextCreate(rawData, width, height, bitsPerComponent, bytesPerRow, colorSpace, kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big);
    
    CGContextDrawImage(context, CGRectMake(0, 0, width, height), imageRef);
    
    CGColorSpaceRelease(colorSpace);
    CGContextRelease(context);
    
    unsigned char * tempRawData = (unsigned char *)malloc(width * height * 3 * sizeof(unsigned char));
    
    for (int i = 0; i < width * height; i ++) {
        
        NSUInteger byteIndex = i * RGBA;
        NSUInteger newByteIndex = i * RGB;
        
        // Get RGB
        CGFloat red    = rawData[byteIndex + 0];
        CGFloat green  = rawData[byteIndex + 1];
        CGFloat blue   = rawData[byteIndex + 2];
        //CGFloat alpha  = rawData[byteIndex + 3];// 这里Alpha值是没有用的
        
        // Set RGB To New RawData
        tempRawData[newByteIndex + 0] = blue;   // B
        tempRawData[newByteIndex + 1] = green;  // G
        tempRawData[newByteIndex + 2] = red;    // R
    }
    
    NSData *data = [NSData dataWithBytes:tempRawData length:(width * height * 3 * sizeof(unsigned char))];
    return data;
}

• Swift5 代码

    func getBGRWithImage(image : UIImage) -> Data? {
        
        let RGBA = 4;
        let RGB  = 3;
        
        let imageRef = image.cgImage!
        
        let width = imageRef.width;
        let height = imageRef.height;
        
        let colorSpace = CGColorSpaceCreateDeviceRGB()
        
        let rawData = malloc(width * height * MemoryLayout<CUnsignedChar>.size * RGBA)!.assumingMemoryBound(to: UInt8.self)
        let bytesPerPixel = RGBA;
        let bytesPerRow = bytesPerPixel * width;
        let bitsPerComponent = 8;
        let bitmapInfo = CGBitmapInfo(
          rawValue: CGBitmapInfo.byteOrder32Big.rawValue | CGImageAlphaInfo.premultipliedLast.rawValue
        )
        let context = CGContext.init(data: rawData, width: width, height: height, bitsPerComponent: bitsPerComponent, bytesPerRow: bytesPerRow, space: colorSpace, bitmapInfo: bitmapInfo.rawValue)
        context?.draw(imageRef, in: CGRect(x: 0, y: 0, width: width, height: height))
        
        let tempRawData = malloc(width * height * 3 * MemoryLayout<CUnsignedChar>.size)!.assumingMemoryBound(to: UInt8.self)
        
        for i in 0..<width * height {
            
            let byteIndex = i * RGBA;
            let newByteIndex = i * RGB;
            
            // Get RGB
            let red    = rawData[byteIndex + 0];
            let green  = rawData[byteIndex + 1];
            let blue   = rawData[byteIndex + 2];
            //CGFloat alpha  = rawData[byteIndex + 3];// 这里Alpha值是没有用的
            
            // Set RGB To New RawData
            tempRawData[newByteIndex + 0] = blue;   // B
            tempRawData[newByteIndex + 1] = green;  // G
            tempRawData[newByteIndex + 2] = red;    // R
        }
        
        let data = Data(bytes: tempRawData, count: (width * height * 3 * MemoryLayout<CUnsignedChar>.size))
        
        return data
    }