CGImageMaskCreate:掩码位/组件无效: 16

Question

我正在更新一个旧的objc项目。我注意到创建图像蒙版在iOS 11和iPhone 7上不起作用

我得到"CGImageMaskCreate: invalid mask bits/component: 16“。警告。如果我将每个组件的位数减少到8(这似乎是最大值)，它可以工作，但我绘制的渐变质量相当差。

下面是我的代码：

- (void)_background:(CGRect)rect
{
    // context for drawing
    CGContextRef context = UIGraphicsGetCurrentContext();

    CGImageRef backgroundimage = CGBitmapContextCreateImage(context);
    CGContextClearRect(context, rect);
    //CGContextDrawImage(context, rect, backgroundimage); 

    // save state
    CGContextSaveGState(context);

    // flip the context (right-sideup)
    CGContextTranslateCTM(context, 0, rect.size.height);
    CGContextScaleCTM(context, 1.0, -1.0);     

    //colors/components/locations
    CGColorSpaceRef colorspace = CGColorSpaceCreateDeviceRGB();
    CGFloat black[4] = {0.0,0.0,0.0,BACKGROUND_ALPHA};
    CGFloat white[4] = {1.0,1.0,1.0,1.0};//clear

    CGFloat components[8] = {

        white[0],white[1],white[2],white[3],        
        black[0],black[1],black[2],black[3],
    };

    CGFloat colorLocations[2] = {0.25,0.5};

    // draw spotlights
    NSInteger spotlightCount = _positionArray.count;
    for (int i=0; i<spotlightCount; ++i)
    {
        // center and radius of spotlight
        CGPoint c = [[_positionArray objectAtIndex:i] CGPointValue];
        CGFloat radius = [[_radiusArray objectAtIndex:i] floatValue];


        CGContextSaveGState(context);

        //add gradient
        //create the gradient Ref
        CGGradientRef gradientRef = CGGradientCreateWithColorComponents(colorspace, components, colorLocations, 2);
        CGContextDrawRadialGradient(context, gradientRef, c, 0.0f, c, radius*2, 0);
        CGGradientRelease(gradientRef);

        CGContextRestoreGState(context);
    }

    CGColorSpaceRelease(colorspace);
    CGContextRestoreGState(context);

    //convert drawing to image for masking
    CGImageRef maskImage = CGBitmapContextCreateImage(context);

    CGImageRef mask = CGImageMaskCreate(CGImageGetWidth(maskImage), 
                                        CGImageGetHeight(maskImage), 
                                        CGImageGetBitsPerComponent(maskImage), 
                                        CGImageGetBitsPerPixel(maskImage), 
                                        CGImageGetBytesPerRow(maskImage), 
                                        CGImageGetDataProvider(maskImage), NULL, NO);

    //      
    //------> CGImageMaskCreate: invalid mask bits/component: 16.
    //

    //mask the background image
    CGImageRef masked = CGImageCreateWithMask(backgroundimage, mask);
    CGImageRelease(backgroundimage);
    //remove the spotlight gradient now that we have it as image
    CGContextClearRect(context, rect);

    //draw the transparent background with the mask
    CGContextDrawImage(context, rect, masked);

    CGImageRelease(maskImage);
    CGImageRelease(mask);
    CGImageRelease(masked);
}

你有什么想法吗？

谢谢。

Answer 1

CGImageMaskCreate的文档描述为“每个组件的图像掩码必须为1、2、4或8位”。