ios - 如何在保持位置、大小和纵横比不变的情况下合并两个 UIImage？

Question

我正在尝试合并两个不同大小的 UIImage。

我的 UIImage A 大小如下:1287 × 1662 像素UIImage B 的大小如下:200 × 200 像素

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我在以下 UIImageView 中显示 A 和 B。

UIImageView backgroundImageView 大小:375 x 667和 UIImageView foregroundImageView 的大小:100 x 100

用户可以将 foregroundImageView 移动到 backgroundImageView 上方的任何位置。

---

这是合并代码:

let previewImage:UIImage? = mergeImages(img: imgBackground.image!, sizeWaterMark: CGRect.init(origin: imgForeground.frame.origin, size: CGSize.init(width: 100, height: 100)), waterMarkImage: imgForeground.image!)

func mergeImages(img:UIImage, sizeWaterMark:CGRect, waterMarkImage:UIImage) -> UIImage {
    let size = self.imgBackground.frame.size
    UIGraphicsBeginImageContextWithOptions(size, false, UIScreen.main.scale)
    img.draw(in: getAspectFitFrame(sizeImgView: size, sizeImage: img.size))
    let frameAspect:CGRect = getAspectFitFrame(sizeImgView: sizeWaterMark.size, sizeImage: waterMarkImage.size)
    let frameOrig:CGRect = CGRect(x: sizeWaterMark.origin.x+frameAspect.origin.x, y: sizeWaterMark.origin.y+frameAspect.origin.y, width: frameAspect.size.width, height: frameAspect.size.height)
    waterMarkImage.draw(in: frameOrig, blendMode: .normal, alpha: 1)
    let result:UIImage = UIGraphicsGetImageFromCurrentImageContext()!
    UIGraphicsEndImageContext()
    return result
}

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 hfactor > vfactor {
        y = (sizeImgView.height - newHeight) / 2
    } else {
        x = (sizeImgView.width - newWidth) / 2
    }
    let newRect:CGRect = CGRect(x: x, y: y, width: newWidth, height: newHeight)
    return newRect
}

这实际上是合并并为我提供了我正在寻找的东西。但它正在减小合并图像的大小。正如您在 mergeImages 函数中看到的这一行。

    let size = self.imgBackground.frame.size

我想要的大小应该是原始 UIImage A 的大小。所以如果我把它改成这样，

    let size = self.imgBackground.image!.size

这将在合并后更改 B 在 A 上的位置。

如需测试，可到here下载查看源码.

我应该怎么做才能保持原始大小不变，同时以适当的纵横比在 A 上准确定位 B？

Answer 1

我将实用程序函数设为静态(最好将它们移动到单独的文件中)以确保它们没有使用 ViewController 实例属性和方法。

在 mergeImages 我删除了:

let size = self.imgBackground.frame.size

并将 size 替换为 img.size。这与您在问题中描述的使用 self.imgBackground.image!.size 相同。

因为源图像和目标图像大小相同，所以不需要调整宽高比，我们只需替换:

img.draw(in: getAspectFitFrame(sizeImgView: size, sizeImage: img.size))

与

img.draw(in: CGRect(origin: CGPoint(x: 0, y: 0), size: img.size))

我还提取了纵横比计算以分离函数 getFactor 以使代码更细化，并使 getAspectFitFrame 不仅返回 CGRect 还返回纵横比(稍后会有用)。

所以效用函数现在看起来像:

static func mergeImages(img: UIImage, sizeWaterMark: CGRect, waterMarkImage: UIImage) -> UIImage {
    UIGraphicsBeginImageContextWithOptions(img.size, false, UIScreen.main.scale)
    img.draw(in: CGRect(origin: CGPoint(x: 0, y: 0), size: img.size))
    let (frameAspect, _) = getAspectFitFrame(from: sizeWaterMark.size, to: waterMarkImage.size)
    let frameOrig = CGRect(x: sizeWaterMark.origin.x + frameAspect.origin.x, y: sizeWaterMark.origin.y + frameAspect.origin.y, width: frameAspect.size.width, height: frameAspect.size.height)
    waterMarkImage.draw(in: frameOrig, blendMode: .normal, alpha: 1)
    let result = UIGraphicsGetImageFromCurrentImageContext()!
    UIGraphicsEndImageContext()
    return result
}

static func getAspectFitFrame(from: CGSize, to: CGSize) -> (CGRect, CGFloat) {
    let (hfactor, vfactor, factor) = ViewController.getFactor(from: from, to: to)

    // Divide the size by the greater of the vertical or horizontal shrinkage factor
    let newWidth = to.width / factor
    let newHeight = to.height / factor

    var x: CGFloat = 0.0
    var y: CGFloat = 0.0

    if hfactor > vfactor {
        y = (from.height - newHeight) / 2
    } else {
        x = (from.width - newWidth) / 2
    }
    return (CGRect(x: x, y: y, width: newWidth, height: newHeight), factor)
}

static func getFactor(from: CGSize, to: CGSize) -> (CGFloat, CGFloat, CGFloat) {
    let hfactor = to.width / from.width
    let vfactor = to.height / from.height
    return (hfactor, vfactor, max(hfactor, vfactor))
}

您还需要另一个效用函数来计算缩放水印的来源和大小:

static func getScaledFrame(from: CGSize, to: CGSize, target: CGRect) -> CGRect {
    let (aspectFitFrame, factor) = ViewController.getAspectFitFrame(from: from, to: to)
    return CGRect(
            origin: CGPoint(
                    x: (target.origin.x - aspectFitFrame.origin.x) * factor,
                    y: (target.origin.y - aspectFitFrame.origin.y) * factor),
            size: CGSize(width: target.width * factor, height: target.height * factor)
    )
}

现在您已准备好渲染合并图像:

    let previewImage = ViewController.mergeImages(
            img: imgBackground.image!,
            sizeWaterMark: ViewController.getScaledFrame(from: imgBackground.frame.size, to: imgBackground.image!.size, target: imgForeground.frame),
            waterMarkImage: imgForeground.image!
    )