將RGB圖像轉換爲灰度和灰度轉換爲RGB圖像？

我已成功將圖像轉換爲灰度，我想將灰度圖像還原爲RGB圖像。請幫忙。提前致謝。將RGB圖像轉換爲灰度和灰度轉換爲RGB圖像？

-(UIImage *) toGrayscale 
    { 

    const int RED = 1; 
    const int GREEN = 2; 
    const int BLUE = 3; 

     Create image rectangle with current image width/height 
     CGRect imageRect = CGRectMake(0, 0, self.size.width * self.scale, self.size.height * self.scale); 

     int width = imageRect.size.width; 
     int height = imageRect.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), [self 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 
       uint8_t gray = (uint8_t) ((30 * rgbaPixel[RED] + 59 * rgbaPixel[GREEN] + 11 * rgbaPixel[BLUE])/100); 

       // 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 
                scale:self.scale 
               orientation:UIImageOrientationUp]; 

     // we're done with image now too 
     CGImageRelease(image); 

     return resultUIImage; 
}

來源

2014-04-17 Arvind

*灰度*到* RGB圖像*？ – nicael

我想將灰度圖像還原爲原始圖像 – Arvind

您應該保留原始圖像並且不要用新的灰度圖像「覆蓋」它。當你再次需要它時，只需使用原始圖像。 –

要回答這個問題有關轉換，您的灰度代碼：

uint8_t gray = (uint8_t) ((30 * rgbaPixel[RED] + 59 * rgbaPixel[GREEN] + 11 * rgbaPixel[BLUE])/100);

給人的關係：

S = 0.3R + 0.59G + 0.11B

GO GO從RGB到S涉及求解一個未知（S）與一個方程（罰款！）。到轉換返回就像嘗試三個未知數（RGB）給出了一個不可能的方程。

一個黑客在做灰階colorisation是考慮灰度剛剛強度，並設定

R = G = B = S - 但這不會正確地恢復你的顏色（顯然）。因此，簡而言之，轉換爲灰度是一種不可逆轉的功能，例如對一個數字進行平方（是正數還是負數？） - 信息丟失，無法檢索。

來源

2014-04-17 13:17:39 dabhaid

將RGB圖像轉換爲灰度和灰度轉換爲RGB圖像？

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