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是的，我知道这听起来像是重复的......但我在他们的开发者页面上尝试了很多示例，甚至是 Apple 的官方代码，这导致 iPhone 4S 和 iPad 3 上出现白色图像。在 iPad 1 和iPhone模拟器虽然。

传递给 convertBitmapRGBA8ToUIImage 的宽度和高度是实际像素，而不是 UIKit 的“点”。即，在 iPad 1 上，它将是 1024、768。在 iPad 3 上，它是 2048、1536。

原始数据缓冲区是从 glReadPixels 读取的 RGBA 数据，并在传递给 tweetMessage() 之前手动翻转。

- (UIImage *) convertBitmapRGBA8ToUIImage:(unsigned char *) buffer
                                withWidth:(int) width
                               withHeight:(int) height {

    CGDataProviderRef ref = CGDataProviderCreateWithData(NULL, buffer, width * height * 4, NULL);
    CGColorSpaceRef colorspace = CGColorSpaceCreateDeviceRGB();
    CGImageRef iref = CGImageCreate(width, height, 8, 32, width * 4, colorspace, kCGBitmapByteOrder32Big | kCGImageAlphaPremultipliedLast, ref, NULL, true, kCGRenderingIntentDefault);

    float scale = 1.0f;
    if ([[UIScreen mainScreen] respondsToSelector:@selector(scale)])
    {
        scale = [[UIScreen mainScreen] scale];
    }

    UIGraphicsBeginImageContextWithOptions(CGSizeMake(width/scale, height/scale), NO, scale);
    CGContextRef cgcontext = UIGraphicsGetCurrentContext();

    CGContextSetBlendMode(cgcontext, kCGBlendModeCopy);

    // Image needs to be flipped BACK for CG
    CGContextTranslateCTM(cgcontext, 0, height/scale);
    CGContextScaleCTM(cgcontext, 1, -1);
    CGContextDrawImage(cgcontext, CGRectMake(0.0, 0.0, width/scale, height/scale), iref);

    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();

    UIGraphicsEndImageContext();

    CFRelease(ref);
    CFRelease(colorspace);
    CGImageRelease(iref);

    return image;
}

- (void)tweetMessage:(const char *)message withURL:(const char *)url withImage:(unsigned char*)rawRGBAImage withWidth:(unsigned int)imageWidth withHeight:(unsigned int)imageHeight
{
    UIImage *tweetImage = nil;
    if (rawRGBAImage != nil)
    {
        // Convert raw data to UIImage
        tweetImage = [self convertBitmapRGBA8ToUIImage:rawRGBAImage withWidth:imageWidth withHeight:imageHeight];
    }
}
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