Walllzzz Walllzzz - 1 month ago 14
Java Question

how to resize Image in java?

Hello I have a QR code Image , and I want to resize it , when I try to resize it to a small image using this code , I always get a blury image , and the QR code is no longer valid when I scan it , but it works fine when I resize to a big sized images with the same code :

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;
}


what is the problem , I don't exactly understand , please give me at least a hint , thank you

A4L A4L
Answer

I use affine transformation to achieve this task, here is my code, hope it helps

/**
 * 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;
}
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