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如何在Java中调整图片大小？

javaimageqr-code
18

你好，我有一个二维码图片，想要将其调整大小。但是，当我使用以下代码将其调整为小尺寸图像时，总会得到模糊的图像，扫描时二维码也不再有效。但是如果我使用相同的代码将其调整为大尺寸图像，则能正常工作：

public BufferedImage getScaledInstance(BufferedImage img,
                                   int targetWidth,
                                   int targetHeight,
                                   Object hint,
                                   boolean higherQuality)
{
int type = (img.getTransparency() == Transparency.OPAQUE) ?
    BufferedImage.TYPE_INT_RGB : BufferedImage.TYPE_INT_ARGB;
BufferedImage ret = (BufferedImage)img;
int w, h;
if (higherQuality) {
    // Use multi-step technique: start with original size, then
    // scale down in multiple passes with drawImage()
    // until the target size is reached
    w = img.getWidth();
    h = img.getHeight();
} else {
    // Use one-step technique: scale directly from original
    // size to target size with a single drawImage() call
    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(w, h, type);
    Graphics2D g2 = tmp.createGraphics();
    g2.setRenderingHint(RenderingHints.KEY_INTERPOLATION, hint);
    //        g2.setRenderingHint(RenderingHints.KEY_DITHERING, hint);
    g2.drawImage(ret, 0, 0, w, h, null);
    g2.dispose();

    ret = tmp;
} while (w != targetWidth || h != targetHeight);

return ret;
}

出了什么问题，我并不完全理解，请至少给我一个提示，谢谢。

你没有展示一个关键的细节 -- 你设置了什么插值提示！ - Sean Owen
非常感谢，我的插值提示是RenderingHints.VALUE_INTERPOLATION_NEAREST_NEIGHBOR，我尝试了所有可能的值，仍然没有起作用。 - Walllzzz
7个回答
32

我使用仿射变换来完成这个任务，以下是我的代码，希望对你有所帮助

/**
 * scale image
 * 
 * @param sbi image to scale
 * @param imageType type of image
 * @param dWidth width of destination image
 * @param dHeight height of destination image
 * @param fWidth x-factor for transformation / scaling
 * @param fHeight y-factor for transformation / scaling
 * @return scaled image
 */
public static BufferedImage scale(BufferedImage sbi, int imageType, int dWidth, int dHeight, double fWidth, double fHeight) {
    BufferedImage dbi = null;
    if(sbi != null) {
        dbi = new BufferedImage(dWidth, dHeight, imageType);
        Graphics2D g = dbi.createGraphics();
        AffineTransform at = AffineTransform.getScaleInstance(fWidth, fHeight);
        g.drawRenderedImage(sbi, at);
    }
    return dbi;
}
非常感谢，它能够工作，但兄弟，fWidth和fHeight应该填什么？每次输出都不同。 - Walllzzz
1
这些是X和Y轴坐标的比例因子，请参见javadoc。例如，如果您想要得到比原始图像half小的结果图像，则将0.5传递给fWidth和fHeight。小于1的值将缩小，大于1的值将放大，1将产生相同尺寸的图像。 - A4L
谢谢，这解决了我的问题。我会选择这个作为被采纳的答案，尽管所有的回答都是被接受的。 - Walllzzz
3
dWidth = sbi.getWidth()*fWidth 和 dHeight = sbi.getHeight()*fHeight。（注：这是一段Java代码，意思是计算原始图片的宽和高分别乘以给定的比例因子后得到的新的宽和高） - caub
1
@A4L 严格来说，将图像大小缩小到原始大小的一半并不简单。例如：如果您有一个尺寸为正方形的图像，将宽度和高度都减少一半将得到一个大小为原始图像的四分之一的图像。您需要应用勾股定理来获得所需的尺寸：缩小c并解出实际所需的高度和宽度的a和b。 - nasukkin
@nasukkin 从技术上讲，你是完全正确的，但一般来说这里的大小大多指的是尺寸的长度。 - A4L
16

基于 @A4L 的回答：

以下是更简单直接的版本。此外，他的解决方案只缩放了画布而没有缩放图像本身。

public static BufferedImage scale(BufferedImage imageToScale, int dWidth, int dHeight) {
        BufferedImage scaledImage = null;
        if (imageToScale != null) {
            scaledImage = new BufferedImage(dWidth, dHeight, imageToScale.getType());
            Graphics2D graphics2D = scaledImage.createGraphics();
            graphics2D.drawImage(imageToScale, 0, 0, dWidth, dHeight, null);
            graphics2D.dispose();
        }
        return scaledImage;
    }

为了提高质量，您可以添加

graphics2D.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR);
graphics2D.setRenderingHint(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY);
graphics2D.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
为了提高质量，一种策略是分几个小步骤进行缩放，直到达到所需的大小。 - A4L
真实的，被称为“渐进式缩放” - 我在这里解释：https://dev59.com/mWAf5IYBdhLWcg3wVxnh#36367652 基于坎贝尔的博客：https://community.oracle.com/docs/DOC-983611 - Patrick
7
我编写了这个类，并且我也经常使用它。我希望代码很直观易懂。
import java.awt.Graphics;
import java.awt.Image;
import java.awt.Toolkit;
import java.awt.image.BufferedImage;
import java.awt.image.CropImageFilter;
import java.awt.image.FilteredImageSource;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import javax.swing.JComponent;


public class ImageScaler {

        private ImageIcon originalImage;
        private ImageIcon scaledImage;

        public ImageScaler(Image image) {
                this.originalImage = new ImageIcon(image);
        }

        public ImageScaler(String fileName) {
                originalImage = new ImageIcon(fileName);
        }

        public void createScaledImage(int size, ScalingDirection scalingDirection) {
                if (scalingDirection == ScalingDirection.HORIZONTAL) {
                        scaledImage = new ImageIcon(originalImage.getImage().getScaledInstance(size, -1, Image.SCALE_SMOOTH));
                } else {
                        scaledImage = new ImageIcon(originalImage.getImage().getScaledInstance(-1, size, Image.SCALE_SMOOTH));
                }       
        }

        public void createScaledImage(int size, ScalingDirection scalingDirection, int scale) {
                if (scalingDirection == ScalingDirection.HORIZONTAL) {
                        scaledImage = new ImageIcon(originalImage.getImage().getScaledInstance(size, -1, scale));
                } else {
                        scaledImage = new ImageIcon(originalImage.getImage().getScaledInstance(-1, size, scale));
                }
        }

        public void createScaledImage(int width, int height, ScaleType scaleType) {
                int imageWidth = originalImage.getImage().getWidth(null);
                int imageHeight = originalImage.getImage().getHeight(null);
                double originalImageRatio = imageWidth / (double) imageHeight;
                double scaledImageRatio = width / (double) height;

                if(scaleType == ScaleType.FIT) {
                        if(imageHeight - (Math.abs(imageWidth - width) / originalImageRatio) <= height) {
                                scaledImage = new ImageIcon(originalImage.getImage().getScaledInstance(width, -1, Image.SCALE_SMOOTH));
                        } else if(imageWidth - (Math.abs(imageHeight - height) * originalImageRatio) <= width) {
                                scaledImage = new ImageIcon(originalImage.getImage().getScaledInstance(-1, height, Image.SCALE_SMOOTH));
                        }
                } else if(scaleType == ScaleType.FILL) {
                        if(imageHeight - (Math.abs(imageWidth - width) / originalImageRatio) >= height) {
                                scaledImage = new ImageIcon(originalImage.getImage().getScaledInstance(width, -1, Image.SCALE_SMOOTH));
                                int thumbHeight = scaledImage.getImage().getHeight(null);

                                // Crop the image
                                scaledImage = new ImageIcon(Toolkit.getDefaultToolkit().createImage(new FilteredImageSource(scaledImage.getImage().getSource(), new CropImageFilter(0, (thumbHeight-height)/2, width, height))));
                        } else if(imageWidth - (Math.abs(imageHeight - height) * originalImageRatio) >= width) {
                                scaledImage = new ImageIcon(originalImage.getImage().getScaledInstance(-1, height, Image.SCALE_SMOOTH));
                                int thumbWidth = scaledImage.getImage().getWidth(null);

                                // Crop the image
                                scaledImage = new ImageIcon(Toolkit.getDefaultToolkit().createImage(new FilteredImageSource(scaledImage.getImage().getSource(), new CropImageFilter((thumbWidth-width)/2, 0, width, height))));
                        }               
                }
        }

        public void saveScaledImage(File file, ImageType imageType) {
                if (scaledImage != null) {
                        BufferedImage bi = new BufferedImage(scaledImage.getIconWidth(), scaledImage.getIconHeight(), BufferedImage.TYPE_INT_RGB);
                        Graphics g = bi.getGraphics();
                        g.drawImage(scaledImage.getImage(), 0, 0, null);
                        try {
                                ImageIO.write(bi, imageType.value(), file);
                        } catch (IOException ioe) {
                                System.out.println("Error occured saving scaled image");
                        }
                } else {
                        System.out.println("Scaled image has not yet been created");
                }
        }

        public void saveOriginalImage(File file, ImageType imageType) {
                if (originalImage != null) {
                        BufferedImage bi = new BufferedImage(originalImage.getIconWidth(), originalImage.getIconHeight(), BufferedImage.TYPE_INT_RGB);
                        Graphics g = bi.getGraphics();
                        g.drawImage(originalImage.getImage(), 0, 0, null);
                        try {
                                ImageIO.write(bi, imageType.value(), file);
                        } catch (IOException ioe) {
                                System.out.println("Error occured saving original image");
                        }
                } else {
                        System.out.println("Original image has not yet been created");
                }
        }

        // ENUMS
        public enum ScalingDirection {VERTICAL, HORIZONTAL};
        public enum ScaleType {FIT, FILL};
        public enum ImageType {
                IMAGE_JPEG ("jpeg"),
                IMAGE_JPG ("jpg"),
                IMAGE_PNG ("png");

                private String value = null;

                ImageType(String value) {
                        this.value = value;
                }

                String value() {
                        return value;
                }
        };
}
谢谢，我没有尝试它，因为上面的代码已经起作用了，让其他人试试吧。 - Walllzzz
2
1
    public static BufferedImage resizeImg(BufferedImage img, int newW, int newH)
    {
    int w = img.getWidth();
    int h = img.getHeight();
    BufferedImage dimg = new BufferedImage(newW, newH, img.getType());
    Graphics2D g = dimg.createGraphics();
    g.setRenderingHint(RenderingHints.KEY_INTERPOLATION,
            RenderingHints.VALUE_INTERPOLATION_BILINEAR);
    g.drawImage(img, 0, 0, newW, newH, 0, 0, w, h, null);
    g.dispose();
    return dimg;      
   }
1
提供更多有关此代码如何解决原帖问题的信息。目前不清楚此代码如何有所帮助。 - aravind
1
0
事实上，解决方案更加简单。您不必创建新的BufferedImage。您可以直接将for3st提到的方法应用于原始的BufferedImage图像（'image'），并设置所需的宽度和高度。因此，只需要一个语句（包含在标准Java文档中）即可。
drawImage(BufferedImage image, int x, int y, int width, int height, ImageObserver observer)
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