IOS中替换一张图片背景颜色的方法

//颜色替换

- (UIImage*) imageToTransparent:(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++)

{

//把绿色变成黑色，把背景色变成透明

if ((*pCurPtr & 0x65815A00) == 0x65815a00) // 将背景变成透明

{

uint8_t* ptr = (uint8_t*)pCurPtr;

ptr[0] = 0;

}

else if ((*pCurPtr & 0x00FF0000) == 0x00ff0000) // 将绿色变成黑色

{

uint8_t* ptr = (uint8_t*)pCurPtr;

ptr[3] = 0; //0~255

ptr[2] = 0;

ptr[1] = 0;

}

else if ((*pCurPtr & 0xFFFFFF00) == 0xffffff00) // 将白色变成透明

{

uint8_t* ptr = (uint8_t*)pCurPtr;

ptr[0] = 0;

}

else

{

// 改成下面的代码，会将图片转成想要的颜色

uint8_t* ptr = (uint8_t*)pCurPtr;

ptr[3] = 0; //0~255

ptr[2] = 0;

ptr[1] = 0;

}

}

// 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;

}

/** 颜色变化 */

void ProviderReleaseData (void *info, const void *data, size_tsize)

{

free((void*)data);

}
http://blog.csdn.net/wutongpiaofei/article/details/37900213