如何调整iOS上的位图

我想调整我正在做的一个项目的位图。 我设法做到这一点，将cgbitmapcontextref转换为像素数组，然后操作像素数组，然后从处理的像素数据中生成一个新的图像。 这种方式非常麻烦。

我想知道是否有任何其他方式来调整CGBitmapContextRef的大小。 谢谢。

Answer 1

如果你没有结婚CGBitmapContextRef ，这里有一些基于UIKit的简单的图片大小调整例程。 此扩展通过裁剪，缩放，方面填充和方面拟合（类似于UIImageView提供的一些主要内容模式）来提供调整图像的大小。

 // // UIImage+Resize.swift // // Image resizing extension // // Created by Robert Ryan on 5/19/11. // Ported to Swift by Robert Ryan on 2/12/15. // Modified for Swift 2 by Robert Ryan on 10/14/15 // // Inspired by http://ofcodeandmen.poltras.com/2008/10/30/undocumented-uiimage-resizing/ // but adjusted to support AspectFill and AspectFit modes. // // Copyright (c) 2015 Robert M. Ryan. All rights reserved. // // This work by Robert M. Ryan is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License. // http://creativecommons.org/licenses/by-sa/4.0/ import UIKit extension UIImage { /// Resize the image to be the required size, stretching it as needed. /// /// - parameter newSize: The new size of the image. /// - parameter contentMode: The `UIViewContentMode` to be applied when resizing image. /// Either `.ScaleToFill`, `.ScaleAspectFill`, or /// `.ScaleAspectFit`. /// /// - returns: Return `UIImage` of resized image. func imageByScalingToSize(newSize: CGSize, contentMode: UIViewContentMode) -> UIImage? { if contentMode == .ScaleToFill { return imageByScalingToFillSize(newSize) } else if contentMode == .ScaleAspectFill || contentMode == .ScaleAspectFit { let horizontalRatio = size.width / newSize.width let verticalRatio = size.height / newSize.height var ratio: CGFloat! if contentMode == .ScaleAspectFill { ratio = min(horizontalRatio, verticalRatio) } else { ratio = max(horizontalRatio, verticalRatio) } let sizeForAspectScale = CGSizeMake(self.size.width / ratio, self.size.height / ratio) let image = imageByScalingToFillSize(sizeForAspectScale) if contentMode == .ScaleAspectFill { let subRect = CGRectMake( floor((sizeForAspectScale.width - newSize.width) / 2.0), floor((sizeForAspectScale.height - newSize.height) / 2.0), newSize.width, newSize.height) return image?.imageByCroppingToBounds(subRect) } return image } return nil } /// Resize the image to be the required size, stretching it as needed. /// /// - parameter newSize: The new size of the image. /// /// - returns: Resized `UIImage` of resized image. func imageByScalingToFillSize(newSize: CGSize) -> UIImage? { UIGraphicsBeginImageContextWithOptions(newSize, false, scale) drawInRect(CGRectMake(0, 0, newSize.width, newSize.height)) let image = UIGraphicsGetImageFromCurrentImageContext() UIGraphicsEndImageContext() return image } /// Crop the image to be the required size. /// /// - parameter bounds: The bounds to which the new image should be cropped. /// /// - returns: Cropped `UIImage`. func imageByCroppingToBounds(bounds: CGRect) -> UIImage? { var rect = bounds rect.size.width *= scale rect.size.height *= scale if let imageRef = CGImageCreateWithImageInRect(CGImage, rect) { return UIImage(CGImage: imageRef, scale: scale, orientation: imageOrientation) } else { return nil } } /// Resize the image to fill the rectange of the specified size, preserving the aspect ratio, trimming if needed. /// /// - parameter newSize: The new size of the image. /// /// - returns: Return `UIImage` of resized image. func imageByScalingAspectFillSize(newSize: CGSize) -> UIImage? { return imageByScalingToSize(newSize, contentMode:.ScaleAspectFill); } /// Resize the image to fit within the required size, preserving the aspect ratio, with no trimming taking place. /// /// - parameter newSize: The new size of the image. /// /// - returns: Return `UIImage` of resized image. func imageByScalingAspectFitSize(newSize: CGSize) -> UIImage? { return imageByScalingToSize(newSize, contentMode:.ScaleAspectFit) } }