调整大小后的图像质量非常低——Java [英] Quality of Image after resize very low -- Java

问题描述

在脚本中，它从大约 300x300 缩小到 60x60.需要提高整体图像质量，因为目前效果很差.

public static Boolean resizeImage(String sourceImg, String destImg, Integer Width, Integer Height, Integer whiteSpaceAmount){BufferedImage origImage;尝试{origImage = ImageIO.read(new File(sourceImg));int type = origImage.getType() == 0?BufferedImage.TYPE_INT_ARGB : origImage.getType();int fHeight = 高度；int fWidth = 宽度；int whiteSpace = 高度 + whiteSpaceAmount;//将所有内容格式化为正方形，因此不需要两个空白计算..双纵横比；//计算调整后的尺寸if (origImage.getHeight() > origImage.getWidth())//如果图片高度大于宽度则适当缩放.{fHeight = 高度；//将高度设置为60，因为它是最大的一侧.aspectRatio = (double)origImage.getWidth()/(double)origImage.getHeight();//获取图片的纵横比.fWidth = (int)Math.round(Width * aspectRatio);//设置通过纵横比创建的宽度.}else if (origImage.getHeight() < origImage.getWidth())//如果图片宽度大于高度适当缩放.{fWidth = 宽度；//将高度设置为60，因为它是最大的一侧.aspectRatio = (double)origImage.getHeight()/(double)origImage.getWidth();//获取图片的纵横比.fHeight = (int)Math.round(Height * aspectRatio);//设置通过纵横比创建的高度.}int extraHeight = whiteSpace - fHeight;int extraWidth = whiteSpace - fWidth;BufferedImage resizedImage = new BufferedImage(whiteSpace, whiteSpace, type);Graphics2D g = resizedImage.createGraphics();g.setColor(Color.white);g.fillRect(0, 0, whiteSpace, whiteSpace);g.setComposite(AlphaComposite.Src);g.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR);g.setRenderingHint(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY);g.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);g.drawImage(origImage, extraWidth/2, extraHeight/2, fWidth, fHeight, null);g.dispose();ImageIO.write(resizedImage, "jpg", new File(destImg));}捕获(IOException 前){返回假；}返回真；}

真的只需要知道我是否可以插入它们以提高质量，或者我是否需要完全查看其他内容.

图片比较.

来源，刚刚从谷歌随机挑选了一台洗衣机.

像这样转换成什么样子.http://imgur.com/8WlXD

解决方案

您看到的问题实际上与用于缩减的重采样过滤器有关.显然，您的库使用的库不适合这种情况.最近邻、双线性和双三次是降尺度时使用的典型坏例子.我不知道 Photoshop 使用的确切重采样过滤器，但我使用了 3-lobed lanczos 并得到了以下结果:

因此，要解决您的问题，您需要使用更智能的重采样过滤器.

In the script it is going from around the 300x300 mark down to 60x60. Need to improve the overall image quality as it is coming out very poorly at the moment.

public static Boolean resizeImage(String sourceImg, String destImg, Integer Width, Integer Height, Integer whiteSpaceAmount) 
{
    BufferedImage origImage;

    try 
    {
        origImage = ImageIO.read(new File(sourceImg));
        int type = origImage.getType() == 0? BufferedImage.TYPE_INT_ARGB : origImage.getType();
        int fHeight = Height;
        int fWidth = Width;
        int whiteSpace = Height + whiteSpaceAmount; //Formatting all to squares so don't need two whiteSpace calcs..
        double aspectRatio;

        //Work out the resized dimensions
        if (origImage.getHeight() > origImage.getWidth()) //If the pictures height is greater than the width then scale appropriately.
        {
            fHeight = Height; //Set the height to 60 as it is the biggest side.

            aspectRatio = (double)origImage.getWidth() / (double)origImage.getHeight(); //Get the aspect ratio of the picture.
            fWidth = (int)Math.round(Width * aspectRatio); //Sets the width as created via the aspect ratio.
        }
        else if (origImage.getHeight() < origImage.getWidth()) //If the pictures width is greater than the height scale appropriately.
        {
            fWidth = Width; //Set the height to 60 as it is the biggest side.

            aspectRatio = (double)origImage.getHeight() / (double)origImage.getWidth(); //Get the aspect ratio of the picture.
            fHeight = (int)Math.round(Height * aspectRatio); //Sets the height as created via the aspect ratio.
        }

        int extraHeight = whiteSpace - fHeight;
        int extraWidth = whiteSpace - fWidth;

        BufferedImage resizedImage = new BufferedImage(whiteSpace, whiteSpace, type);
        Graphics2D g = resizedImage.createGraphics();
        g.setColor(Color.white);
        g.fillRect(0, 0, whiteSpace, whiteSpace);

        g.setComposite(AlphaComposite.Src);
        g.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR);
        g.setRenderingHint(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY);
        g.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);

        g.drawImage(origImage, extraWidth/2, extraHeight/2, fWidth, fHeight, null);
        g.dispose();

        ImageIO.write(resizedImage, "jpg", new File(destImg));
    } 
    catch (IOException ex) 
    {
        return false;
    }

    return true;
}

Really just need to know if their is something I can plug in that will bump up the quality or if I need to look at something else entirely.

EDIT: Picture comparison.

Source, just picked a random washing machine from google. http://www.essexappliances.co.uk/images/categories/washing-machine.jpg

The same picture converted in Photoshop to what I need it to be. http://imgur.com/78B1p

What it looks like being converted like this. http://imgur.com/8WlXD

解决方案

The issue you are seeing is actually related to the resampling filter used for downscaling. Obviously, the one used by your library is a bad one for the situation. Nearest neighbor, bilinear and bicubic are typical bad examples to be used when downscaling. I don't know the exact resampling filter Photoshop uses, but I used 3-lobed lanczos and got the following result:

So, to solve your problem, you need to use a smarter resampling filter.

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