如何解决如何缩小UIImage并使其同时变脆/清晰而不是模糊？
| 我需要按比例缩小图像，但要采用清晰的方式。例如，在Photoshop中，图像尺寸缩小选项为“ Bicubic Smoother”（模糊）和“ Bicubic Sharper”。 这个图像缩小算法是在某个地方开源或记录的，还是SDK提供了这样做的方法？解决方法
仅使用
imageWithCGImage
- (UIImage *)resizeImage:(UIImage*)image newSize:(CGSize)newSize {
CGRect newRect = CGRectIntegral(CGRectMake(0,newSize.width,newSize.height));
CGImageRef imageRef = image.CGImage;
UIGraphicsBeginImageContextWithOptions(newSize,NO,0);
CGContextRef context = UIGraphicsGetCurrentContext();
// Set the quality level to use when rescaling
CGContextSetInterpolationQuality(context,kCGInterpolationHigh);
CGAffineTransform flipVertical = CGAffineTransformMake(1,-1,newSize.height);
CGContextConcatCTM(context,flipVertical);
// Draw into the context; this scales the image
CGContextDrawImage(context,newRect,imageRef);
// Get the resized image from the context and a UIImage
CGImageRef newImageRef = CGBitmapContextCreateImage(context);
UIImage *newImage = [UIImage imageWithCGImage:newImageRef];
CGImageRelease(newImageRef);
UIGraphicsEndImageContext();
return newImage;
}
func resizeImage(image: UIImage,newSize: CGSize) -> (UIImage) {
let newRect = CGRectIntegral(CGRectMake(0,newSize.height))
let imageRef = image.CGImage
UIGraphicsBeginImageContextWithOptions(newSize,false,0)
let context = UIGraphicsGetCurrentContext()
// Set the quality level to use when rescaling
CGContextSetInterpolationQuality(context,kCGInterpolationHigh)
let flipVertical = CGAffineTransformMake(1,newSize.height)
CGContextConcatCTM(context,flipVertical)
// Draw into the context; this scales the image
CGContextDrawImage(context,imageRef)
let newImageRef = CGBitmapContextCreateImage(context) as CGImage
let newImage = UIImage(CGImage: newImageRef)
// Get the resized image from the context and a UIImage
UIGraphicsEndImageContext()
return newImage
}
func resizeImage(image: UIImage,newHeight: CGFloat) -> UIImage {
let scale = newHeight / image.size.height
let newWidth = image.size.width * scale
UIGraphicsBeginImageContext(CGSizeMake(newWidth,newHeight))
image.drawInRect(CGRectMake(0,newWidth,newHeight))
let newImage = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
return newImage
}
+ (UIImage *)imageWithCGImage:(CGImageRef)imageRef scale:(CGFloat)scale orientation:(UIImageOrientation)orientation
func resizeImage(image: UIImage,newSize: CGSize) -> (UIImage) {
let newRect = CGRect(x: 0,y: 0,width: newSize.width,height: newSize.height).integral
UIGraphicsBeginImageContextWithOptions(newSize,0)
let context = UIGraphicsGetCurrentContext()
// Set the quality level to use when rescaling
context!.interpolationQuality = CGInterpolationQuality.default
let flipVertical = CGAffineTransform(a: 1,b: 0,c: 0,d: -1,tx: 0,ty: newSize.height)
context!.concatenate(flipVertical)
// Draw into the context; this scales the image
context?.draw(image.cgImage!,in: CGRect(x: 0.0,y: 0.0,width: newRect.width,height: newRect.height))
let newImageRef = context!.makeImage()! as CGImage
let newImage = UIImage(cgImage: newImageRef)
// Get the resized image from the context and a UIImage
UIGraphicsEndImageContext()
return newImage
}
- (UIImage *)resizeImageProportionallyIntoNewSize:(CGSize)newSize;
{
CGFloat scaleWidth = 1.0f;
CGFloat scaleHeight = 1.0f;
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;
}
}
//prepare source and target image
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
// A proportionally scaled image by cutting of the image overlay
UIGraphicsBeginImageContext(newSize);
//Center image point so that on each egde is a little cutoff
CGRect thumbnailRect = CGRectZero;
thumbnailRect.size.width = newSize.width * scaleWidth;
thumbnailRect.size.height = 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 ;
}
extension UIImage {
func thumbnail(ofSize proposedSize: CGSize) -> UIImage? {
let scale = min(size.width/proposedSize.width,size.height/proposedSize.height)
let newSize = CGSize(width: size.width/scale,height: size.height/scale)
let newOrigin = CGPoint(x: (proposedSize.width - newSize.width)/2,y: (proposedSize.height - newSize.height)/2)
let thumbRect = CGRect(origin: newOrigin,size: newSize).integral
UIGraphicsBeginImageContextWithOptions(proposedSize,0)
draw(in: thumbRect)
let result = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
return result
}
}
extension UIImage {
func resized(By coefficient:CGFloat) -> UIImage? {
guard coefficient >= 0 && coefficient <= 1 else {
print(\"The coefficient must be a floating point number between 0 and 1\")
return nil
}
let newWidth = size.width * coefficient
let newHeight = size.height * coefficient
UIGraphicsBeginImageContext(CGSize(width: newWidth,height: newHeight))
draw(in: CGRect(x: 0,width: newWidth,height: newHeight))
let newImage = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
return newImage
}
}
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