UIImageJPEGRepresentation在视网膜显示器上提供2x图像
我有这个代码，它创建一个图像，然后添加一些效果，并将其缩小以制作largeThumbnail 。
UIImage *originalImage = [UIImage imageWithData:self.originalImage]; thumbnail = createLargeThumbnailFromImage(originalImage); NSLog(@"thumbnail: %f", thumbnail.size.height); NSData *thumbnailData = UIImageJPEGRepresentation(thumbnail, 1.0);
稍后的：
UIImage *image = [UIImage imageWithData:self.largeThumbnail]; NSLog(@"thumbnail 2: %f", image.size.height);
NSLog返回：
thumbnail: 289.000000 thumbnail 2: 578.000000
正如您所看到的，当它将数据从数据转换回来时，它的大小是它的2倍。 任何想法为什么会这样？
大缩略图代码：
UIImage *createLargeThumbnailFromImage(UIImage *image) { UIImage *resizedImage; resizedImage = [image imageScaledToFitSize:LARGE_THUMBNAIL_SIZE]; CGRect largeThumbnailRect = CGRectMake(0, 0, resizedImage.size.width, resizedImage.size.height); UIGraphicsBeginImageContextWithOptions(resizedImage.size, NO, 0); CGContextRef context = UIGraphicsGetCurrentContext(); //Image CGContextTranslateCTM(context, 0, resizedImage.size.height); CGContextScaleCTM(context, 1.0, -1.0); CGContextDrawImage(context, largeThumbnailRect, resizedImage.CGImage); //Border CGContextSaveGState(context); CGRect innerRect = rectForRectWithInset(largeThumbnailRect, 1.5); CGMutablePathRef borderPath = createRoundedRectForRect(innerRect, 0); CGContextSetStrokeColorWithColor(context, [[UIColor whiteColor] CGColor]); CGContextSetLineWidth(context, 3); CGContextAddPath(context, borderPath); CGContextStrokePath(context); CGContextRestoreGState(context); UIImage *thumbnail = UIGraphicsGetImageFromCurrentImageContext(); UIGraphicsEndImageContext(); return thumbnail; }
尝试替换加载第二张图像的部分：
UIImage *image = [UIImage imageWithData:self.largeThumbnail];
与这一个：
UIImage *jpegImage = [UIImage imageWithData:self.largeThumbnail]; UIImage *image = [UIImage imageWithCGImage:jpegImage.CGImage scale:originalImage.scale orientation:jpegImage.imageOrientation];
这里发生的是未设置图像比例，因此您获得双图像尺寸。