假设我在 UIViewController 上有一个 UIImage 的对象,我想从 Controller 设置图像。基本上我想做的是,将两张图片合并在一起,第一张图片是蓝色的 5 星:
第二张图片是灰色的 5 星:
它用于对图像进行评级。由于最大评分是 5,那么我必须将它乘以 20 得到 100 分,以便于计算。更多细节逻辑请看代码。
所以我有这个(BM_RatingHelper.swift):
static func getRatingImageBasedOnRating(rating: CGFloat, width: CGFloat, height: CGFloat) -> UIImage {
// available maximum rating is 5.0, so we have to multiply it by 20 to achieve 100.0 point
let ratingImageWidth = ( width / 100.0 ) * ( rating * 20.0 )
// get active rating image
let activeRatingImage = BM_ImageHelper.resize(UIImage(named: "StarRatingFullActive")!, targetSize: CGSize(width: width, height: height))
let activeRatingImageView = UIImageView(frame: CGRectMake(0, 0, ratingImageWidth, height));
activeRatingImageView.image = BM_ImageHelper.crop(activeRatingImage, x: 0, y: 0, width: ratingImageWidth, height: height);
// get inactive rating image
let inactiveRatingImage = BM_ImageHelper.resize(UIImage(named: "StarRatingFullInactive")!, targetSize: CGSize(width: width, height: height))
let inactiveRatingImageView = UIImageView(frame: CGRectMake(ratingImageWidth, 0, ( 100.0 - ratingImageWidth ), height));
inactiveRatingImageView.image = BM_ImageHelper.crop(inactiveRatingImage, x: ratingImageWidth, y: 0, width: ( 100.0 - ratingImageWidth ), height: height);
// combine the images
let ratingView = UIView.init(frame: CGRect(x: 0, y: 0, width: width, height: height))
ratingView.backgroundColor = BM_Color.colorForType(BM_ColorType.ColorWhiteTransparent)
ratingView.addSubview(activeRatingImageView)
ratingView.addSubview(inactiveRatingImageView)
return ratingView.capture()
}
BM_ImageHelper.swift
:
import UIKit
class BM_ImageHelper: NSObject {
// http://stackoverflow.com/questions/158914/cropping-an-uiimage
static func crop(image: UIImage, x: CGFloat, y: CGFloat, width: CGFloat, height: CGFloat) -> UIImage {
let rect = CGRect(x: x, y: y, width: width, height: height)
let imageRef = CGImageCreateWithImageInRect(image.CGImage, rect)!
let croppedImage = UIImage(CGImage: imageRef)
return croppedImage
}
// http://iosdevcenters.blogspot.com/2015/12/how-to-resize-image-in-swift-in-ios.html
static func resize(image: UIImage, targetSize: CGSize) -> UIImage {
let size = image.size
let widthRatio = targetSize.width / image.size.width
let heightRatio = targetSize.height / image.size.height
// Figure out what our orientation is, and use that to form the rectangle
var newSize: CGSize
if(widthRatio > heightRatio) {
newSize = CGSizeMake(size.width * heightRatio, size.height * heightRatio)
} else {
newSize = CGSizeMake(size.width * widthRatio, size.height * widthRatio)
}
// This is the rect that we've calculated out and this is what is actually used below
let rect = CGRectMake(0, 0, newSize.width, newSize.height)
// Actually do the resizing to the rect using the ImageContext stuff
UIGraphicsBeginImageContextWithOptions(newSize, false, 1.0)
image.drawInRect(rect)
let newImage = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
return newImage
}
}
extension UIView {
// http://stackoverflow.com/a/34895760/897733
func capture() -> UIImage {
UIGraphicsBeginImageContextWithOptions(self.frame.size, self.opaque, UIScreen.mainScreen().scale)
self.layer.renderInContext(UIGraphicsGetCurrentContext()!)
let image = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
return image
}
}
我调用该函数(假设需要填充的图像是 ratingImage
):
self.ratingImage.image =
BM_RatingHelper.getRatingImageBasedOnRating(3.7, width: 100.0, height: 20.0)
代码运行完美,但合并后的图像质量太低,尽管我使用了高质量图像。这是 3.7 评级的图像:
我应该怎么做才能在不损失原始质量的情况下合并图像?谢谢。
最佳答案
在您的 BM_ImageHelper.resize
方法中,它给出了比例 1.0。它应该是设备的屏幕比例。
改成
UIGraphicsBeginImageContextWithOptions(newSize, false, UIScreen.mainScreen().scale)
更新
同时更改裁剪方法以解决比例问题,例如
static func crop(image: UIImage, x: CGFloat, y: CGFloat, width: CGFloat, height: CGFloat) -> UIImage {
let transform = CGAffineTransformMakeScale(image.scale, image.scale)
let rect = CGRect(x: x, y: y, width: width, height: height)
let transformedCropRect = CGRectApplyAffineTransform(rect, transform);
let imageRef = CGImageCreateWithImageInRect(image.CGImage, transformedCropRect)!
let croppedImage = UIImage(CGImage: imageRef, scale: image.scale, orientation: image.imageOrientation)
return croppedImage
}
关于ios - 调整大小和裁剪 2 个图像影响原始图像质量,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/35788458/