Re-sizing an image without losing quality

Question

I made this code to resize images with two factors. It works, but the quality of image is very bad after it is resized! Can you help me?

This is the code

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Answer 1

All the methods posted does'nt work for me i have to reduce QrCode size, but with above methods the quality is poor and scanner doesn't work , if i take original picture and resize it in paint the scanner is working.

Answer 2

If your image source is a png then use like this:

Image imgSmall = imgBig.getScaledInstance(
        targetWidth, targetHeight, Image.SCALE_SMOOTH);

If you want to resize jpeg or gif without loose too much quality, I made a library in 2010 for this: beautylib on github that uses internally this other library: java-image-scaling. You can see directly the source code to find something useful: https://github.com/felipelalli/beautylib/blob/master/src/br/eti/fml/beautylib/ResizeImage.java

Answer 3

Yes, I had the same problems and solved them, please read my question (answer is embedded in the question). I tried imgscalr and java-image-scaling libraries and found the second much better quality. Get close to the monitor to appreciate the difference between the thumbnail examples.

Despite my initial thoughts, resizing an image seems a very complicate thing, you don't want to do it yourself. For example I tell java-image-scaling to use ResampleFilters.getLanczos3Filter() to have better result.

It also addresses how to save a JPG with a quality higher than the standard 75, which produces a bad result especially for a thumbnail.

I also wrote a small class, called MyImage to help with common tasks, such as reading an image from a byte array, from a file, scaling by specifying only width or only height, scaling by specifying a bounding box, scaling by specifying width and height and adding a white band to make the image not distorted and writing to JPG file.

Answer 4

None of the answers will help you to get real quality you desire. Include thumbailator.jar in your project (download it form here):

https://code.google.com/p/thumbnailator/

https://code.google.com/p/thumbnailator/wiki/Downloads?tm=2

Then upload the image first (as file, without Thumbnailator - it's use is to create thumbs, but you can create large images with it of course), and resize it to every dimensions you want (with Thumbnailator 800x600 for example). Quality will be very good. I was searching for this long time, this .jar helped me to achieve what i want.

Answer 5

The do while loop used in The Perils of Image.getScaledInstance() will run into an infinite loop, given those values, w = 606; h = 505, targetWidth = 677, targetHeight = 505

Here is a simplied testing code, you can try it.

public class LoopTest {

    public static void main(String[] args) {
        new LoopTest(true, 606, 505, 677, 505);
    }

    public LoopTest(boolean higherQuality, int w, int h, int targetWidth, int targetHeight) {
        do {
            if (higherQuality && w > targetWidth) {
                w /= 2;
                if (w < targetWidth) {
                    w = targetWidth;
                }
            }

            if (higherQuality && h > targetHeight) {
                h /= 2;
                if (h < targetHeight) {
                    h = targetHeight;
                }
            }
        } while (w != targetWidth || h != targetHeight);        // TODO Auto-generated constructor stub
    }
}

A quick work around: define an index for loop count. If the index is >=10, break out of loop.

Answer 6

Answer: Remove the hints VALUE_INTERPOLATION_BILINEAR, and VALUE_RENDERING_QUALITY.

Example:

public static BufferedImage resizeImage(BufferedImage image, int width, int height) {

    // Temporary image

    BufferedImage tmp = image;

    // Result image

    BufferedImage result = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);

    // Graphics object

    Graphics2D graphics = (Graphics2D)result.createGraphics();

    // Add rendering hints

    graphics.setRenderingHint(RenderingHints.KEY_COLOR_RENDERING, RenderingHints.VALUE_COLOR_RENDER_QUALITY);
    graphics.setRenderingHint(RenderingHints.KEY_DITHERING, RenderingHints.VALUE_DITHER_ENABLE);

    // Draw tmp

    graphics.drawImage(tmp, 0, 0, width, height, null);

    // Dispose of graphics object

    graphics.dispose();

    // Return image result

    return result;
}

Note: For some reason, the hints VALUE_INTERPOLATION_BILINEAR and VALUE_RENDERING_QUALITY blur the image being resized.