swift – NSImage在我绘制文本时调整大小

我有以下代码在NSImage上绘制文本.
但是当我将其保存到磁盘时,生成的图像会调整为较小的图像.

我做错了什么？请指教

func drawText(image :NSImage) ->NSImage
{
    let text = "Sample Text"
    let font = NSFont.boldSystemFont(ofSize: 18)
    let imageRect = CGRect(x: 0,y: 0,width: image.size.width,height: image.size.height)

    let textRect = CGRect(x: 5,y: 5,width: image.size.width - 5,height: image.size.height - 5)
    let textStyle = NSMutableParagraphStyle.default().mutableCopy() as! NSMutableParagraphStyle
    let textFontAttributes = [
        NSFontAttributeName: font,NSForegroundColorAttributeName: NSColor.white,NSParagraphStyleAttributeName: textStyle
    ]

    let im:NSImage = NSImage(size: image.size)

    let rep:NSBitmapImageRep = NSBitmapImageRep(bitmapDataPlanes: nil,pixelsWide: Int(image.size.width),pixelsHigh: Int(image.size.height),bitsPerSample: 8,samplesPerPixel: 4,hasAlpha: true,isPlanar: false,colorSpaceName: NSCalibratedRGBColorSpace,bytesPerRow: 0,bitsPerPixel: 0)!

    im.addRepresentation(rep)

    im.lockFocus()

    image.draw(in: imageRect)
    text.draw(in: textRect,withAttributes: textFontAttributes)

    im.unlockFocus()

    return im
}

这是一种不同的方法,使用临时NSView绘制图像和文本并将结果缓存到新图像中(代码是Swift 4).你不需要处理像素的好处

class ImageView : NSView  {

    var image : NSImage
    var text : String

    init(image: NSImage,text: String)
    {
        self.image = image
        self.text = text
        super.init(frame: NSRect(origin: NSZeroPoint,size: image.size))
    }

    required init?(coder decoder: NSCoder) { fatalError() }

    override func draw(_ dirtyRect: NSRect) {
        let font = NSFont.boldSystemFont(ofSize: 18)
        let textRect = CGRect(x: 5,height: image.size.height - 5)
        image.draw(in: dirtyRect)
        text.draw(in: textRect,withAttributes: [.font: font,.foregroundColor: NSColor.white])
    }

    var outputImage : NSImage  {
        let imageRep = bitmapImageRepForCachingDisplay(in: frame)!
        cacheDisplay(in: frame,to:imageRep)
        let tiffData = imageRep.tiffRepresentation!
        return NSImage(data : tiffData)!
    }
}

要使用它,请初始化视图

let image = ... // get some image
let view = ImageView(image: image,text: "Sample Text")

并获得新的图像

let imageWithText = view.outputImage

注意：

段落样式根本不使用,但如果你想创建一个可变段落样式,只需写入

let textStyle = NSMutableParagraphStyle()

原文链接：/swift/319975.html

swift – NSImage在我绘制文本时调整大小

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