调整 UIImage 大小导致 UIImage 的数据大小增加答案

【问题标题】：Resizing UIImage Causes UIImage's Data Size Increase调整 UIImage 大小导致 UIImage 的数据大小增加
【发布时间】：2015-11-20 02:53:34
【问题描述】：

我正在尝试使用 NYXImageKit 调整 UIImage 的大小，这会导致图像的数据大小增加

P.S.: originalImage 的尺寸是 1024 * 1024

var originalImage = image; 
//originalImage SIZE 108 KB
var resizedImage = image.scaleToFillSize(CGSize(width: 256, height: 256)); 
//resizedImage BECAME 620 KB

有什么想法吗？

以下代码来自 NYXImageKit 类 UIImage+Resizing.m

-(UIImage*)scaleToFillSize:(CGSize)newSize
{
    size_t destWidth = (size_t)(newSize.width * self.scale);
    size_t destHeight = (size_t)(newSize.height * self.scale);
    if (self.imageOrientation == UIImageOrientationLeft
        || self.imageOrientation == UIImageOrientationLeftMirrored
        || self.imageOrientation == UIImageOrientationRight
        || self.imageOrientation == UIImageOrientationRightMirrored)
    {
        size_t temp = destWidth;
        destWidth = destHeight;
        destHeight = temp;
    }

  /// Create an ARGB bitmap context
    CGContextRef bmContext = NYXCreateARGBBitmapContext(destWidth, destHeight, destWidth * kNyxNumberOfComponentsPerARBGPixel, NYXImageHasAlpha(self.CGImage));
    if (!bmContext)
        return nil;

    /// Image quality
    CGContextSetShouldAntialias(bmContext, true);
    CGContextSetAllowsAntialiasing(bmContext, true);
    CGContextSetInterpolationQuality(bmContext, kCGInterpolationHigh);

    /// Draw the image in the bitmap context

    UIGraphicsPushContext(bmContext);
  CGContextDrawImage(bmContext, CGRectMake(0.0f, 0.0f, destWidth, destHeight), self.CGImage);
    UIGraphicsPopContext();

    /// Create an image object from the context
    CGImageRef scaledImageRef = CGBitmapContextCreateImage(bmContext);
    UIImage* scaled = [UIImage imageWithCGImage:scaledImageRef scale:self.scale orientation:self.imageOrientation];

    /// Cleanup
    CGImageRelease(scaledImageRef);
    CGContextRelease(bmContext);

    return scaled;
}

【问题讨论】：

scaleToFillSize (CGSize size)的邮政编码以及您使用的是什么类型的图片？
已编辑。请检查@HarvantS。
Image quality 添加是原因。
好的，请问我应该如何编辑代码@HarvantS。
我已经调整大小并压缩了大约 240K 的 jpeg 数据，然后重构为 UIImage(data:)，然后它的 jpeg 数据变成了大约 600K！我已经考虑了点大小和像素大小，它们都是正确的。我认为 UIImage(data:) 实际上做了一些平滑等使图像数据更大。

标签： ios objective-c swift uiimage nsdata

【解决方案1】：

希望对你有帮助

public func resizeImage(width width: CGFloat, height: CGFloat) -> UIImage {

    let newSize: CGRect = CGRectMake(0, 0, width, height)
    UIGraphicsBeginImageContext(newSize.size)
    self.drawInRect(newSize)
    let resizedImage: UIImage = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()

    return resizedImage
}

【讨论】：

感谢您的回复，但您提供的代码没有正确调整大小，导致质量非常差。

【解决方案2】：

Swift Image Resizer

import UIKit

func RBSquareImageTo(image: UIImage, size: CGSize) -> UIImage {
    return RBResizeImage(RBSquareImage(image), size)
}

func RBSquareImage(image: UIImage) -> UIImage {
    var originalWidth  = image.size.width
    var originalHeight = image.size.height

    var edge: CGFloat
    if originalWidth > originalHeight {
        edge = originalHeight
    } else {
        edge = originalWidth
    }

    var posX = (originalWidth  - edge) / 2.0
    var posY = (originalHeight - edge) / 2.0

    var cropSquare = CGRectMake(posX, posY, edge, edge)

    var imageRef = CGImageCreateWithImageInRect(image.CGImage, cropSquare);
    return UIImage(CGImage: imageRef, scale: UIScreen.mainScreen().scale, orientation: image.imageOrientation)
}

func RBResizeImage(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
}

【讨论】：

好的。让我试试，如果我有其他解决方案，稍后会通知你。