UIImge去掉黑色背景-----

- (UIImage*) imageBlackToTransparent:(UIImage*) image
{
// 分配内存
const int imageWidth = image.size.width;
const int imageHeight = image.size.height;
size_t      bytesPerRow = imageWidth * 4;
uint32_t* rgbImageBuf = (uint32_t*)malloc(bytesPerRow * imageHeight);

// 创建context
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGContextRef context = CGBitmapContextCreate(rgbImageBuf, imageWidth, imageHeight, 8, bytesPerRow, colorSpace,
kCGBitmapByteOrder32Little | kCGImageAlphaNoneSkipLast);
CGContextDrawImage(context, CGRectMake(0, 0, imageWidth, imageHeight), image.CGImage);

// 遍历像素
int pixelNum = imageWidth * imageHeight;
uint32_t* pCurPtr = rgbImageBuf;
for (int i = 0; i < pixelNum; i++, pCurPtr++)
{
if ((*pCurPtr & 0xFFFFFF00) == 0)    // 将黑色变成透明
{
uint8_t* ptr = (uint8_t*)pCurPtr;
ptr[0] = 0;
}

// 改成下面的代码，会将图片转成灰度
/*uint8_t* ptr = (uint8_t*)pCurPtr;
// gray = red * 0.11 + green * 0.59 + blue * 0.30
uint8_t gray = ptr[3] * 0.11 + ptr[2] * 0.59 + ptr[1] * 0.30;
ptr[3] = gray;
ptr[2] = gray;
ptr[1] = gray;*/
}

// 将内存转成image
CGDataProviderRef dataProvider = CGDataProviderCreateWithData(NULL, rgbImageBuf, bytesPerRow * imageHeight,ProviderReleaseData);
CGImageRef imageRef = CGImageCreate(imageWidth, imageHeight, 8, 32, bytesPerRow, colorSpace,
kCGImageAlphaLast | kCGBitmapByteOrder32Little, dataProvider,
NULL, true, kCGRenderingIntentDefault);
CGDataProviderRelease(dataProvider);

UIImage* resultUIImage = [UIImage imageWithCGImage:imageRef];

// 释放
CGImageRelease(imageRef);
CGContextRelease(context);
CGColorSpaceRelease(colorSpace);
// free(rgbImageBuf) 创建dataProvider时已提供释放函数，这里不用free

return resultUIImage;
}
void ProviderReleaseData (void *info, const void *data, size_t size)
{
free((void*)data);
}