调整后的图像质量非常低 - Java

Question

在脚本中,它从大约300x300标记下降到60x60.需要提高整体图像质量,因为它目前非常糟糕.

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;
}

真的只需要知道他们是否可以插入它会提高质量或者我是否需要完全看待其他东西.

编辑:图片比较.

来源,刚刚从谷歌挑选一台随机洗衣机. http://www.essexappliances.co.uk/images/categories/washing-machine.jpg

在Photoshop中将相同的图片转换为我需要的图片. http://imgur.com/78B1p

像这样转换的样子. http://imgur.com/8WlXD

Answer 1

在大范围内缩小图像本质上是危险的(从质量的角度来看),尤其是使用单个步骤.

推荐的方法是使用分而治之的方法.基本上,您可以按50%的步长缩小图像,直到达到所需的大小.

所以,我拍摄了650x748的原始图像并将其缩小到适合60x60区域(52x60)

与一步相比分而治之......

public class TestImageResize {

    public static void main(String[] args) {
        new TestImageResize();
    }

    public TestImageResize() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (Exception ex) {
                }

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setLayout(new BorderLayout());
                frame.add(new ScalePane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class ScalePane extends JPanel {

        private BufferedImage original;
        private BufferedImage scaled;

        public ScalePane() {
            try {
                original = ImageIO.read(new File("path/to/master.jpg"));
                scaled = getScaledInstanceToFit(original, new Dimension(60, 60));
                ImageIO.write(scaled, "jpg", new File("scaled.jpg"));

                BufferedImage image = new BufferedImage(52, 60, BufferedImage.TYPE_INT_RGB);
                Graphics2D g2d = image.createGraphics();
                g2d.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR);
                g2d.setRenderingHint(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY);
                g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
                g2d.drawImage(original, 0, 0, 52, 60, this);
                g2d.dispose();

                ImageIO.write(image, "jpg", new File("test.jpg"));

            } catch (IOException ex) {
                ex.printStackTrace();
            }
        }

        @Override
        public Dimension getPreferredSize() {

            Dimension size = super.getPreferredSize();
            if (original != null) {
                if (scaled != null) {
                    size.width = original.getWidth() + scaled.getWidth();
                    size.height = original.getHeight();
                } else {
                    size.width = original.getWidth();
                    size.height = original.getHeight();
                }
            }

            return size;
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            Graphics2D g2d = (Graphics2D) g.create();
            g2d.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR);
            g2d.setRenderingHint(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY);
            g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);

            if (original != null) {
                int x = 0;
                int y = (getHeight() - original.getHeight()) / 2;;
                if (scaled != null) {
                    x = (getWidth() - (original.getWidth() + scaled.getWidth())) / 2;
                } else {
                    x = (getWidth() - original.getWidth()) / 2;
                }
                g2d.drawImage(original, x, y, this);

                if (scaled != null) {
                    x += original.getWidth();
                    y = (getHeight() - scaled.getHeight()) / 2;
                    g2d.drawImage(scaled, x, y, this);
                }
            }
            g2d.dispose();
        }

        public BufferedImage getScaledInstanceToFit(BufferedImage img, Dimension size) {
            float scaleFactor = getScaleFactorToFit(img, size);
            return getScaledInstance(img, scaleFactor);
        }

        public float getScaleFactorToFit(BufferedImage img, Dimension size) {
            float scale = 1f;
            if (img != null) {
                int imageWidth = img.getWidth();
                int imageHeight = img.getHeight();
                scale = getScaleFactorToFit(new Dimension(imageWidth, imageHeight), size);
            }
            return scale;
        }

        public float getScaleFactorToFit(Dimension original, Dimension toFit) {
            float scale = 1f;
            if (original != null && toFit != null) {
                float dScaleWidth = getScaleFactor(original.width, toFit.width);
                float dScaleHeight = getScaleFactor(original.height, toFit.height);
                scale = Math.min(dScaleHeight, dScaleWidth);
            }
            return scale;
        }

        public float getScaleFactor(int iMasterSize, int iTargetSize) {
            float scale = 1;
            if (iMasterSize > iTargetSize) {
                scale = (float) iTargetSize / (float) iMasterSize;
            } else {
                scale = (float) iTargetSize / (float) iMasterSize;
            }
            return scale;
        }

        public BufferedImage getScaledInstance(BufferedImage img, double dScaleFactor) {
            BufferedImage imgBuffer = null;
            imgBuffer = getScaledInstance(img, dScaleFactor, RenderingHints.VALUE_INTERPOLATION_BILINEAR, true);
            return imgBuffer;
        }

        protected BufferedImage getScaledInstance(BufferedImage img, double dScaleFactor, Object hint, boolean higherQuality) {

            int targetWidth = (int) Math.round(img.getWidth() * dScaleFactor);
            int targetHeight = (int) Math.round(img.getHeight() * dScaleFactor);

            int type = (img.getTransparency() == Transparency.OPAQUE)
                            ? BufferedImage.TYPE_INT_RGB : BufferedImage.TYPE_INT_ARGB;

            BufferedImage ret = (BufferedImage) img;

            if (targetHeight > 0 || targetWidth > 0) {
                int w, h;
                if (higherQuality) {
                    w = img.getWidth();
                    h = img.getHeight();
                } else {
                    w = targetWidth;
                    h = targetHeight;
                }

                do {
                    if (higherQuality && w > targetWidth) {
                        w /= 2;
                        if (w < targetWidth) {
                            w = targetWidth;
                        }
                    }

                    if (higherQuality && h > targetHeight) {
                        h /= 2;
                        if (h < targetHeight) {
                            h = targetHeight;
                        }
                    }

                    BufferedImage tmp = new BufferedImage(Math.max(w, 1), Math.max(h, 1), type);
                    Graphics2D g2 = tmp.createGraphics();
                    g2.setRenderingHint(RenderingHints.KEY_INTERPOLATION, hint);
                    g2.drawImage(ret, 0, 0, w, h, null);
                    g2.dispose();

                    ret = tmp;
                } while (w != targetWidth || h != targetHeight);
            } else {
                ret = new BufferedImage(1, 1, type);
            }
            return ret;
        }
    }
}

您也可以找到感兴趣的Image.getScaledInstance()的Perils

Answer 2

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,你的图书馆使用的那个对于这种情况是不好的.最小邻居,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3瓣lanczos并得到以下结果:

因此,要解决您的问题,您需要使用更智能的重采样过滤器.

Answer 3

荷兰人,这就是我维护imgscalr库的原因 - 让这种东西变得非常容易.

在您的示例中,单个方法调用将在您的第一个ImageIO.read行之后立即执行操作:

origImage = ImageIO.read(new File(sourceImg));

您可以执行以下操作以获得所需内容(此方法的javadoc):

origImage = Scalr.resize(origImage, Method.ULTRA_QUALITY, 60);

如果它仍然看起来有点锯齿(因为你从图像中删除了这么多信息,你可以在命令中添加以下OP来对图像应用光抗锯齿滤镜,使其看起来更平滑):

origImage = Scalr.resize(origImage, Method.ULTRA_QUALITY, 60, Scalr.OP_ANTIALIAS);

这将取代你拥有的所有其余代码逻辑.我建议的另一件事就是将你真正的小样本保存为PNG,这样就不会对图像进行压缩/有损转换,或者如果你真的想要JPG格式,请确保你在JPG上使用很少甚至没有压缩.(这是一篇关于如何做的文章 ;它使用了ImageWriteParam类)

imgscalr根据Apache 2许可证授权并托管在GitHub上,因此您可以随心所欲地使用它; 如果您在服务器端应用程序中使用库并排队大量的扩展操作并且不想终止服务器,它还包括异步扩展支持.

Answer 4

如前所述,Java的Graphics2D没有提供非常好的缩减算法.如果您不想自己实现复杂的算法,可以尝试专门用于此的当前开源库:Thumbnailator,imgscalr和ImageMagick的Java接口.

在研究私人项目的过程中,我尝试了它们(除了ImageMagick),以下是用Photoshop作为参考的视觉效果:

A. 具有默认设置的Thumbnailator 0.4.8(无内部调整大小)
B. 使用ULTRA_QUALTY设置的imgscalr 4.2
C. Photoshop CS5双三次过滤器(另存为web)
D.带有所有HQ渲染提示的Graphics2d

这是使用过的代码

Thumbnailator和PS创造了类似的结果,而imgscalr似乎更软.其中一个库创造了更好的结果是主观的.另一点需要考虑的是性能.虽然Thumbnailator和Graphics2d具有相似的运行时,但在我的基准测试中,imgscalr相当慢(使用ULTRA_QUALITY).

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