如何在运行时过滤颜色?——iphone

Question

我有一个图像，其中每个像素都有三种原色(RGBA)之一。我需要在运行时通过改变颜色通道来改变图像(运行时使用滤镜)我有。pvr和相应的glTexture2D，但我如何在运行时过滤/改变颜色?我不能使用OpenGL ES 2.0但我可以使用Cocos2D和OpenGL ES 1.x(

Answer 1

这不是微不足道的，但它可能对您有用:

// Convierte la imagen a blanco y negro
+ (UIImage *)convertImageToGrayScale:(UIImage *)i {
    CGSize size = [i size];
    int width = size.width;
    int height = size.height;
    // the pixels will be painted to this array
    uint32_t *pixels = (uint32_t *) malloc(width * height * sizeof(uint32_t));
    // clear the pixels so any transparency is preserved
    memset(pixels, 0, width * height * sizeof(uint32_t));
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    // create a context with RGBA pixels
    CGContextRef context = CGBitmapContextCreate(pixels, width, height, 8, width * sizeof(uint32_t), colorSpace, 
                                                 kCGBitmapByteOrder32Little | kCGImageAlphaPremultipliedLast);
    // paint the bitmap to our context which will fill in the pixels array
    CGContextDrawImage(context, CGRectMake(0, 0, width, height), [i CGImage]);
    for(int y = 0; y < height; y++) {
        for(int x = 0; x < width; x++) {
            uint8_t *rgbaPixel = (uint8_t *) &pixels[y * width + x];
            // convert to grayscale using recommended method: http://en.wikipedia.org/wiki/Grayscale#Converting_color_to_grayscale
            uint32_t gray = 0.3 * rgbaPixel[RED] + 0.59 * rgbaPixel[GREEN] + 0.11 * rgbaPixel[BLUE];
            // set the pixels to gray
            rgbaPixel[RED] = gray;
            rgbaPixel[GREEN] = gray;
            rgbaPixel[BLUE] = gray;
        }
    }
    // create a new CGImageRef from our context with the modified pixels
    CGImageRef image = CGBitmapContextCreateImage(context);
    // we're done with the context, color space, and pixels
    CGContextRelease(context);
    CGColorSpaceRelease(colorSpace);
    free(pixels);
    // make a new UIImage to return
    UIImage *resultUIImage = [UIImage imageWithCGImage:image];
    // we're done with image now too
    CGImageRelease(image);
    return resultUIImage;
}

将接收到的UIimage转换为灰度图像

Answer 2

这是我用来操作RGBA图片的代码

-(UIImage*)convertGrayScaleImageRedImage:(CGImageRef)inImage{
CFDataRef m_DataRef = CGDataProviderCopyData(CGImageGetDataProvider(inImage));  
UInt8 * m_PixelBuf = (UInt8 *) CFDataGetBytePtr(m_DataRef);  
int length = CFDataGetLength(m_DataRef);
for (int i=0; i<length; i+=4){
    int r = i;
    int g = i+1;
    int b = i+2;
    //int a = i+3;//alpha
    NSLog(@"r=%i, g=%i, b=%i",m_PixelBuf[r], m_PixelBuf[g], m_PixelBuf[b]);

    m_PixelBuf[r] = 1;
    m_PixelBuf[g] = 0;  
    m_PixelBuf[b] = 0;  
    //m_PixelBuf[a] = m_PixelBuf[a];//alpha
}  
CGContextRef ctx = CGBitmapContextCreate(m_PixelBuf,  
                                         CGImageGetWidth(inImage),  
                                         CGImageGetHeight(inImage),  
                                         CGImageGetBitsPerComponent(inImage),
                                         CGImageGetBytesPerRow(inImage),  
                                         CGImageGetColorSpace(inImage),  
                                         CGImageGetBitmapInfo(inImage) 
                                         ); 
CGImageRef imageRef = CGBitmapContextCreateImage(ctx);  
CGContextRelease(ctx);
UIImage *redImage = [UIImage imageWithCGImage:imageRef];
CGImageRelease(imageRef);
return redImage;
}