我在UIImage
上写了一个类别,用于调整iphone照片应用等图片的大小。
虽然Interpolation设置为高,但图像看起来并不像照片应用程序中的图像。相反,它会显示unsharp
或blurry
。
这是我做的:
- (UIImage *)resizeImageProportionallyIntoNewSize:(CGSize)newSize;
{
CGFloat scaleWidth = 1.0f;
CGFloat scaleHeight = 1.0f;
NSLog(@"Origin Size = %@", NSStringFromCGSize(self.size));
if (CGSizeEqualToSize(self.size, newSize) == NO) {
//calculate "the longer side"
if(self.size.width > self.size.height) {
scaleWidth = self.size.width / self.size.height;
} else {
scaleHeight = self.size.height / self.size.width;
}
}
// now draw the new image in a context with scaling proportionally
UIImage *sourceImage = self;
UIImage *newImage = nil;
//now we create a context in newSize and draw the image out of the bounds of the context to get
//an proportionally scaled image by cutting of the image overlay
if([[UIScreen mainScreen] scale] == 2.00) {
UIGraphicsBeginImageContextWithOptions(newSize, YES, 2.0);
}
UIGraphicsBeginImageContext(newSize);
// Set the quality level to use when rescaling
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetInterpolationQuality(context, kCGInterpolationHigh);
//Center image point so that on each egde is a little cutoff
CGRect thumbnailRect = CGRectZero;
thumbnailRect.size.width = (int) newSize.width * scaleWidth;
thumbnailRect.size.height = (int) newSize.height * scaleHeight;
thumbnailRect.origin.x = (int) (newSize.width - thumbnailRect.size.width) * 0.5;
thumbnailRect.origin.y = (int) (newSize.height - thumbnailRect.size.height) * 0.5;
[sourceImage drawInRect:thumbnailRect];
newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
if(newImage == nil) NSLog(@"could not scale image");
return newImage ;
}
BTW:使用高插值没有区别。也许我做错了什么。
提前感谢您的帮助!
答案 0 :(得分:2)
制作缩略图的最佳方法是使用Image I / O Framework让系统为您完成。唯一的技巧是,因为你使用CGImage,你必须考虑屏幕分辨率:
CGImageSourceRef src = CGImageSourceCreateWith... // whatever
CGFloat scale = [UIScreen mainScreen].scale;
CGFloat w = // maximum size, multiplied by the scale
NSDictionary* d =
[NSDictionary dictionaryWithObjectsAndKeys:
(id)kCFBooleanTrue, kCGImageSourceShouldAllowFloat,
(id)kCFBooleanTrue, kCGImageSourceCreateThumbnailWithTransform,
(id)kCFBooleanTrue, kCGImageSourceCreateThumbnailFromImageAlways,
[NSNumber numberWithInt:(int)w], kCGImageSourceThumbnailMaxPixelSize,
nil];
CGImageRef imref =
CGImageSourceCreateThumbnailAtIndex(src, 0, (__bridge CFDictionaryRef)d);
UIImage* im =
[UIImage imageWithCGImage:imref scale:scale orientation:UIImageOrientationUp];
CFRelease(imref); CFRelease(src);
答案 1 :(得分:0)
如果不清晰/模糊,您应该尝试通过以下方式关闭消除锯齿:
CGContextSetShouldAntialias(context, NO);
希望这会有所帮助。