Question

我正在使用以下代码对我加载的图像执行一些操作，但我发现当它在视网膜显示器上时显示变得模糊

- (UIImage*)createImageSection:(UIImage*)image section:(CGRect)section

{
float originalWidth = image.size.width ;
float originalHeight = image.size.height ;
int w = originalWidth * section.size.width;
int h = originalHeight * section.size.height;

CGContextRef ctx = CGBitmapContextCreate(nil, w, h, 8, w * 8,CGImageGetColorSpace([image CGImage]), kCGImageAlphaPremultipliedLast);
CGContextClearRect(ctx, CGRectMake(0, 0, originalWidth * section.size.width, originalHeight * section.size.height)); // w + h before
CGContextTranslateCTM(ctx, (float)-originalWidth * section.origin.x, (float)-originalHeight * section.origin.y);
CGContextDrawImage(ctx, CGRectMake(0, 0, originalWidth, originalHeight), [image CGImage]);
CGImageRef cgImage = CGBitmapContextCreateImage(ctx);
UIImage* resultImage = [[UIImage alloc] initWithCGImage:cgImage];

CGContextRelease(ctx);
CGImageRelease(cgImage);

return resultImage;
}

如何更改此选项以使其与视网膜兼容。

提前感谢您的帮助

最佳， DV

Answer 1

CGImages没有考虑您设备的Retina-ness，所以您必须自己这样做。

要做到这一点，您需要将所有在CoreGraphics例程中使用的坐标和大小乘以输入图像的scale属性（在Retina设备上为2.0），以确保您在双重决议。

然后，您需要将resultImage的初始化更改为使用initWithCGImage:scale:orientation:并输入相同的比例因子。这就是Retina设备以原始分辨率渲染输出而不是像素加倍分辨率的原因。

Answer 2

感谢您的回答，帮帮我！无论如何要更清楚，OP的代码应该像这样改变：

- (UIImage*)createImageSection:(UIImage*)image section:(CGRect)section        
{
    CGFloat scale = [[UIScreen mainScreen] scale]; ////// ADD

    float originalWidth = image.size.width ;
    float originalHeight = image.size.height ;
    int w = originalWidth * section.size.width *scale; ////// CHANGE
    int h = originalHeight * section.size.height *scale; ////// CHANGE

    CGContextRef ctx = CGBitmapContextCreate(nil, w, h, 8, w * 8,CGImageGetColorSpace([image CGImage]), kCGImageAlphaPremultipliedLast);
    CGContextClearRect(ctx, CGRectMake(0, 0, originalWidth * section.size.width, originalHeight * section.size.height)); // w + h before
    CGContextTranslateCTM(ctx, (float)-originalWidth * section.origin.x, (float)-originalHeight * section.origin.y);

    CGContextScaleCTM(UIGraphicsGetCurrentContext(), scale, scale); ////// ADD

    CGContextDrawImage(ctx, CGRectMake(0, 0, originalWidth, originalHeight), [image CGImage]);
    CGImageRef cgImage = CGBitmapContextCreateImage(ctx);
    UIImage* resultImage = [[UIImage alloc] initWithCGImage:cgImage];

    CGContextRelease(ctx);
    CGImageRelease(cgImage);

    return resultImage;
}

Answer 3

Swift版本：

    let scale = UIScreen.mainScreen().scale

    CGContextScaleCTM(UIGraphicsGetCurrentContext(), scale, scale)

用于视网膜显示的CoreGraphics

3 个答案: