UIView提供了“等比缩放”内容模式。但是，我已经继承了UIView，并想使用drawInRect以等比例缩放的方式绘制UIImage。是否有任何方法可以让我在不使用UIImageView的情况下访问该功能？
UIView提供了“等比例缩放”（aspect fit）内容模式。但是，如果您已经子类化了UIView并希望使用drawInRect按照等比例缩放的方式绘制UIImage，则是否有任何方法可以在不使用UIImageView的情况下访问该功能呢？6个回答
41
那个的数学计算有点复杂，但幸运的是，我之前准备过一种解决方案：
- (UIImage *)imageScaledToSize:(CGSize)size
{
//create drawing context
UIGraphicsBeginImageContextWithOptions(size, NO, 0.0f);
//draw
[self drawInRect:CGRectMake(0.0f, 0.0f, size.width, size.height)];
//capture resultant image
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return image;
}
- (UIImage *)imageScaledToFitSize:(CGSize)size
{
//calculate rect
CGFloat aspect = self.size.width / self.size.height;
if (size.width / aspect <= size.height)
{
return [self imageScaledToSize:CGSizeMake(size.width, size.width / aspect)];
}
else
{
return [self imageScaledToSize:CGSizeMake(size.height * aspect, size.height)];
}
}
- Nick Lockwood
6
37
您需要在提供的矩形中绘制。
Swift:
func AVMakeRect(aspectRatio: CGSize, insideRect boundingRect: CGRect) -> CGRect
Objective-C:
CGRect AVMakeRectWithAspectRatioInsideRect(CGSize aspectRatio, CGRect boundingRect);
请参阅文档
它能够保留纵横比并使绘图居中。
它适用于所有情况。
- Antzi
2
1这绝对是最好的解决方案，只需记得在使用它时
import AVFoundation。 - Patru这节省了我很多时间 - 谢谢！我在绘图上下文中为通知（UNNotificationAttachment）缩放SVG资源时遇到了问题；它们总是被裁剪或不能保持纵横比。我尝试了各种手动计算，但都无济于事。这个方法很有效！ - Chris
14
这是解决方案
CGSize imageSize = yourImage.size;
CGSize viewSize = CGSizeMake(450, 340); // size in which you want to draw
float hfactor = imageSize.width / viewSize.width;
float vfactor = imageSize.height / viewSize.height;
float factor = fmax(hfactor, vfactor);
// Divide the size by the greater of the vertical or horizontal shrinkage factor
float newWidth = imageSize.width / factor;
float newHeight = imageSize.height / factor;
CGRect newRect = CGRectMake(xOffset,yOffset, newWidth, newHeight);
[image drawInRect:newRect];
-- 来自 https://dev59.com/oHI-5IYBdhLWcg3wu7FU#1703210 的解答
一个关于等比缩放的替代方案
-(CGSize ) getImageSize :(CGSize )imgViewSize andActualImageSize:(CGSize )actualImageSize {
// imgViewSize = size of view in which image is to be drawn
// actualImageSize = size of image which is to be drawn
CGSize drawImageSize;
if (actualImageSize.height > actualImageSize.width) {
drawImageSize.height = imgViewSize.height;
drawImageSize.width = actualImageSize.width/actualImageSize.height * imgViewSize.height;
}else {
drawImageSize.width = imgViewSize.width;
drawImageSize.height = imgViewSize.width * actualImageSize.height / actualImageSize.width;
}
return drawImageSize;
}
Swift 3.0 的代码：
func getAspectFitFrame(sizeImgView:CGSize, sizeImage:CGSize) -> CGRect{
let imageSize:CGSize = sizeImage
let viewSize:CGSize = sizeImgView
let hfactor : CGFloat = imageSize.width/viewSize.width
let vfactor : CGFloat = imageSize.height/viewSize.height
let factor : CGFloat = max(hfactor, vfactor)
// Divide the size by the greater of the vertical or horizontal shrinkage factor
let newWidth : CGFloat = imageSize.width / factor
let newHeight : CGFloat = imageSize.height / factor
var x:CGFloat = 0.0
var y:CGFloat = 0.0
if newWidth > newHeight{
y = (sizeImgView.height - newHeight)/2
}
if newHeight > newWidth{
x = (sizeImgView.width - newWidth)/2
}
let newRect:CGRect = CGRect(x: x, y: y, width: newWidth, height: newHeight)
return newRect
}
- Haider
4
这里有一个CGSize的扩展帮助类，您可能会发现它很有用：
extension CGSize
{
func sizeThatFitsSize(_ aSize: CGSize) -> CGSize
{
let width = min(self.width * aSize.height / self.height, aSize.width)
return CGSize(width: width, height: self.height * width / self.width)
}
}
在-drawInRect:的实现中，我们应该做以下操作：
let imageSizeThatFitsViewBounds = self.image.size.sizeThatFitsSize(self.bounds.size)
let imageRectX = (self.bounds.size.width - imageSizeThatFitsViewBounds.width) / 2
let imageRectY = (self.bounds.size.height - imageSizeThatFitsViewBounds.height) / 2
let imageRect = CGRect(origin: CGPoint(x: imageRectX, y: imageRectY), size: imageSizeThatFitsViewBounds)
- Russian
2
这可能对您有所帮助，请试一试
UIImage *logoImage = [UIImage imageNamed:@"logo.png"];
float newHeight = ((logoImage.size.height / logoImage.size.width) * 100.0);
CGRect newLogoImageRect = CGRectMake(0, 0, 80.0, newHeight);
[logoImage drawInRect:newLogoImageRect];
请将100.0替换为您的最大高度，80.0替换为您的最大宽度。
- Nathan
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// 返回图像。 - gblazex