图像在Java中调整大小以减小图像大小 [英] Image Resizing in Java to reduce image size

问题描述

我有一张说尺寸为800x800的图片，尺寸为170 kb。我想调整此图像的大小，说600x600。调整大小后，我希望减少图像大小。我该怎么做？

I have an Image of say dimensions 800x800 which has a size of 170 kb. I want to resize this image to say 600x600. After resizing i want the image size to be reduced. How can i do this?

推荐答案

您不需要一个完整的图像处理库来简单地调整图像大小。

You don't need a full blown Image processing library for simply resizing an image.

推荐的方法是使用渐进双线性缩放，就像这样（随意使用此代码中的方法）：

The recommended approach is by using progressive bilinear scaling, like so (feel free to use this method as is in your code):

public BufferedImage scale(BufferedImage img, int targetWidth, int targetHeight) {

    int type = (img.getTransparency() == Transparency.OPAQUE) ? BufferedImage.TYPE_INT_RGB : BufferedImage.TYPE_INT_ARGB;
    BufferedImage ret = img;
    BufferedImage scratchImage = null;
    Graphics2D g2 = null;

    int w = img.getWidth();
    int h = img.getHeight();

    int prevW = w;
    int prevH = h;

    do {
        if (w > targetWidth) {
            w /= 2;
            w = (w < targetWidth) ? targetWidth : w;
        }

        if (h > targetHeight) {
            h /= 2;
            h = (h < targetHeight) ? targetHeight : h;
        }

        if (scratchImage == null) {
            scratchImage = new BufferedImage(w, h, type);
            g2 = scratchImage.createGraphics();
        }

        g2.setRenderingHint(RenderingHints.KEY_INTERPOLATION,
                RenderingHints.VALUE_INTERPOLATION_BILINEAR);
        g2.drawImage(ret, 0, 0, w, h, 0, 0, prevW, prevH, null);

        prevW = w;
        prevH = h;
        ret = scratchImage;
    } while (w != targetWidth || h != targetHeight);

    if (g2 != null) {
        g2.dispose();
    }

    if (targetWidth != ret.getWidth() || targetHeight != ret.getHeight()) {
        scratchImage = new BufferedImage(targetWidth, targetHeight, type);
        g2 = scratchImage.createGraphics();
        g2.drawImage(ret, 0, 0, null);
        g2.dispose();
        ret = scratchImage;
    }

    return ret;

}

在肮脏的富客户端。

基于在您的评论中，您可以降低质量并编码JPEG字节，如下所示：

Based on your comment, you can reduce quality and encode JPEG bytes like so:

image 是BufferedImage。

image is the BufferedImage.

ByteArrayOutputStream os = new ByteArrayOutputStream();
ImageWriter writer = (ImageWriter) ImageIO.getImageWritersByFormatName("jpeg").next();

ImageWriteParam param = writer.getDefaultWriteParam();
param.setCompressionMode(ImageWriteParam.MODE_EXPLICIT);
param.setCompressionQuality(0.2f); // Change this, float between 0.0 and 1.0

writer.setOutput(ImageIO.createImageOutputStream(os));
writer.write(null, new IIOImage(image, null, null), param);
writer.dispose();

现在，因为 os 是 ByteArrayOutputStream ，你可以对它进行Base64编码。

Now, since os is a ByteArrayOutputStream, you can Base64 encode it.

String base64 = Base64.encode(os.toByteArray());

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