[英]Resizing an Image by preserving aspect ratio in swift
我有以下扩展名来调整图像大小。
extension NSImage {
func resizeImage(width: CGFloat, _ height: CGFloat) -> NSImage {
let img = NSImage(size: CGSize(width:width, height:height))
img.lockFocus()
let ctx = NSGraphicsContext.current()
ctx?.imageInterpolation = .high
self.draw(in: NSMakeRect(0, 0, width, height), from: NSMakeRect(0, 0, size.width, size.height), operation: .copy, fraction: 1)
img.unlockFocus()
return img
}
}
调整尺寸时,不会保留宽高比。
如何修改代码以保留宽高比?
请指教。
更新:
这是C#中使用的逻辑。我不知道如何快速执行此操作。
double ratioX = (double) canvasWidth / (double) originalWidth;
double ratioY = (double) canvasHeight / (double) originalHeight;
// use whichever multiplier is smaller
double ratio = ratioX < ratioY ? ratioX : ratioY;
// now we can get the new height and width
int newHeight = Convert.ToInt32(originalHeight * ratio);
int newWidth = Convert.ToInt32(originalWidth * ratio);
// Now calculate the X,Y position of the upper-left corner
// (one of these will always be zero)
int posX = Convert.ToInt32((canvasWidth - (originalWidth * ratio)) / 2);
int posY = Convert.ToInt32((canvasHeight - (originalHeight * ratio)) / 2);
您可以更改方法签名,使其使用百分比而不是大小来缩放图像:
extension NSImage {
func resizedTo(width: CGFloat, height: CGFloat) -> NSImage {
let ratioX = width / size.width
let ratioY = height / size.height
let ratio = ratioX < ratioY ? ratioX : ratioY
let canvasSize = NSSize(width: size.width * ratio, height: size.height * ratio)
let img = NSImage(size: canvasSize)
img.lockFocus()
NSGraphicsContext.current?.imageInterpolation = .high
draw(in: NSRect(origin: CGPoint(x: (canvasSize.width - (size.width * ratio)) / 2, y: (canvasSize.height - (size.height * ratio)) / 2), size: canvasSize), from: NSRect(origin: .zero, size: size), operation: .copy, fraction: 1)
img.unlockFocus()
return img
}
func resizedTo(percentage: CGFloat) -> NSImage {
let canvasSize = CGSize(width: size.width * percentage, height: size.height * percentage)
let img = NSImage(size: canvasSize)
img.lockFocus()
NSGraphicsContext.current?.imageInterpolation = .high
draw(in: NSRect(origin: .zero, size: canvasSize), from: NSRect(origin: .zero, size: size), operation: .copy, fraction: 1)
img.unlockFocus()
return img
}
func resizedTo(width: CGFloat) -> NSImage {
let canvasSize = CGSize(width: width, height: CGFloat(ceil(width/size.width * size.height)))
let img = NSImage(size: canvasSize)
img.lockFocus()
NSGraphicsContext.current?.imageInterpolation = .high
draw(in: NSRect(origin: .zero, size: canvasSize), from: NSRect(origin: .zero, size: size), operation: .copy, fraction: 1)
img.unlockFocus()
return img
}
}
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