当我在上面绘制文本时，NSImage 会调整大小 [英] NSImage Getting Resized when I draw Text on it

问题描述

我有以下代码在 NSImage 上绘制文本.但是当我将它保存到磁盘时，生成的图像被调整为较小的图像.

I have the following code to draw a text over an NSImage. But the resulting image is getting resized to smaller one when I save it to disk.

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
}

推荐答案

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

This is a different approach using a temporary NSView to draw the image and the text and cache the result in a new image (code is Swift 4). The benefit it you don't need to deal with pixels

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, y: 5, width: image.size.width - 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，请初始化一个视图

To use it, initialize a view

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

并获取新图像

let imageWithText = view.outputImage

<小时>

注意:

段落样式根本不用，但是如果你想创建一个可变的段落样式就写

The paragraph style is not used at all, but if you want to create a mutable paragraph style just write

let textStyle = NSMutableParagraphStyle()

这篇关于当我在上面绘制文本时，NSImage 会调整大小的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！