iphone – 以编程方式反转图像的颜色可能吗？

概述我想在iOS中拍摄图像并反转颜色。 要扩展quixoto的答案，并且因为我有一个项目的相关源代码，如果你需要下载到CPU像素的 *** 作，那么我已经添加了exposition到以下，应该做的诀窍： @implementation UIImage (NegativeImage)- (UIImage *)negativeImage{ // get width and height as int 我想在iOS中拍摄图像并反转颜色。解决方法 要扩展quixoto的答案，并且因为我有一个项目的相关源代码，如果你需要下载到cpu像素的 *** 作，那么我已经添加了exposition到以下，应该做的诀窍：

@implementation UIImage (NegativeImage)- (UIImage *)negativeImage{    // get wIDth and height as integers,since we'll be using them as    // array subscripts,etc,and this'll save a whole lot of casting    CGSize size = self.size;    int wIDth = size.wIDth;    int height = size.height;    // Create a suitable RGB+Alpha bitmap context in BGRA colour space    CGcolorSpaceRef colourSpace = CGcolorSpaceCreateDeviceRGB();    unsigned char *memoryPool = (unsigned char *)calloc(wIDth*height*4,1);    CGContextRef context = CGBitmapContextCreate(memoryPool,wIDth,height,8,wIDth * 4,colourSpace,kCGBitmapByteOrder32Big | kCGImageAlphaPremultiplIEdLast);    CGcolorSpaceRelease(colourSpace);    // draw the current image to the newly created context    CGContextDrawImage(context,CGRectMake(0,height),[self CGImage]);    // run through every pixel,a scan line at a time...    for(int y = 0; y < height; y++)    {        // get a pointer to the start of this scan line        unsigned char *linePointer = &memoryPool[y * wIDth * 4];        // step through the pixels one by one...        for(int x = 0; x < wIDth; x++)        {            // get RGB values. We're dealing with premultiplIEd Alpha            // here,so we need to divIDe by the Alpha channel (if it            // isn't zero,of course) to get uninflected RGB. We            // multiply by 255 to keep precision while still using            // integers            int r,g,b;             if(linePointer[3])            {                r = linePointer[0] * 255 / linePointer[3];                g = linePointer[1] * 255 / linePointer[3];                b = linePointer[2] * 255 / linePointer[3];            }            else                r = g = b = 0;            // perform the colour inversion            r = 255 - r;            g = 255 - g;            b = 255 - b;            // multiply by Alpha again,divIDe by 255 to undo the            // scaling before,store the new values and advance            // the pointer we're reading pixel data from            linePointer[0] = r * linePointer[3] / 255;            linePointer[1] = g * linePointer[3] / 255;            linePointer[2] = b * linePointer[3] / 255;            linePointer += 4;        }    }    // get a CG image from the context,wrap that into a    // UIImage    CGImageRef cgImage = CGBitmapContextCreateImage(context);    UIImage *returnImage = [UIImage imageWithCGImage:cgImage];    // clean up    CGImageRelease(cgImage);    CGContextRelease(context);    free(memoryPool);    // and return    return returnImage;}@end

所以这样添加一个类别方法给UIImage：

>创建一个清晰的CoreGraphics位图上下文，可以访问它的内存把UIImage拉到它>遍历每个像素，从预乘α转换为未反映的RGB，分别反转每个通道，再次乘以Alpha并存储回>从上下文获取图像并将其包装成UIImage>自己清理，并返回UIImage

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