如何根据RGB值生成UIImage，暂时用不到这些，记录一下。

http://www.cocoachina.com/bbs/read.php?tid-60270.html http://stackoverflow.com/questions/845278/overlaying-a-uiimage-with-a-color  如何根据RGB值生成UIImage，暂时用不到这些，记录一下。

1  先定义UIColor *color = [[UIColor alloc] initWithRed:xxx/255.0f green:xxx/255.0f blue:xxx/255.0f alpha:1.0];   //xxx为RGB的值

2  然后[view setBackgroundColor:color];

3  截图 
            //获取图像
            [刚才的的view.layer renderInContext:UIGraphicsGetCurrentContext()];
            UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
            UIGraphicsEndImageContext();
存image就是你要的 了  

- (CGContextRef) createARGBBitmapContextFromImage:(CGImageRef) inImage {

    CGContextRef    context = NULL;
    CGColorSpaceRef colorSpace;
    void *          bitmapData;
    int             bitmapByteCount;
    int             bitmapBytesPerRow;

    // Get image width, height. We'll use the entire image.
    size_t pixelsWide = CGImageGetWidth(inImage);
    size_t pixelsHigh = CGImageGetHeight(inImage);

    // Declare the number of bytes per row. Each pixel in the bitmap in this
    // example is represented by 4 bytes; 8 bits each of red, green, blue, and
    // alpha.
    bitmapBytesPerRow   = (pixelsWide * 4);
    bitmapByteCount     = (bitmapBytesPerRow * pixelsHigh);

    // Use the generic RGB color space.
    colorSpace = CGColorSpaceCreateDeviceRGB();

    if (colorSpace == NULL)
    {
        fprintf(stderr, "Error allocating color space\n");
        return NULL;
    }

    // Allocate memory for image data. This is the destination in memory
    // where any drawing to the bitmap context will be rendered.
    bitmapData = malloc( bitmapByteCount );
    if (bitmapData == NULL)
    {
        fprintf (stderr, "Memory not allocated!");
        CGColorSpaceRelease( colorSpace );
        return NULL;
    }

    // Create the bitmap context. We want pre-multiplied ARGB, 8-bits
    // per component. Regardless of what the source image format is
    // (CMYK, Grayscale, and so on) it will be converted over to the format
    // specified here by CGBitmapContextCreate.
    context = CGBitmapContextCreate (bitmapData,
                                                                     pixelsWide,
                                                                     pixelsHigh,
                                                                     8,      // bits per component
                                                                     bitmapBytesPerRow,
                                                                     colorSpace,
                                                                     kCGImageAlphaPremultipliedFirst);
    if (context == NULL)
    {
        free (bitmapData);
        fprintf (stderr, "Context not created!");
    }

    // Make sure and release colorspace before returning
    CGColorSpaceRelease( colorSpace );

    return context;
} 

然后：
- (id)initWithCGImage:(CGImageRef)imageRef;