How to convert an image into a transparent image i

问题:

How to convert a white background of an image into a transparent background? Can anyone tel me how to do this?

回答1:

The first result from Google is this:

Make a color transparent http://www.rgagnon.com/javadetails/java-0265.html

It makes the Blue part of an image transparent, but I'm sure you can adapt that to use White intstead

(hint: Pass Color.WHITE to the makeColorTransparent function, instead of Color.BLUE)

Found a more complete and modern answer here: How to make a color transparent in a BufferedImage and save as PNG

回答2:

This method will make background transparent. You need to pass the image you want to modify, colour, and tolerance.

final int color = ret.getRGB(0, 0);
final Image imageWithTransparency = makeColorTransparent(ret, new Color(color), 10);
final BufferedImage transparentImage = imageToBufferedImage(imageWithTransparency);

private static BufferedImage imageToBufferedImage(final Image image) {
        final BufferedImage bufferedImage =
            new BufferedImage(image.getWidth(null), image.getHeight(null), BufferedImage.TYPE_INT_ARGB);
        final Graphics2D g2 = bufferedImage.createGraphics();
        g2.drawImage(image, 0, 0, null);
        g2.dispose();
        return bufferedImage;
}


private static Image makeColorTransparent(final BufferedImage im, final Color color, int tolerance) {
    int temp = 0;

    if (tolerance < 0 || tolerance > 100) {

        System.err.println("The tolerance is a percentage, so the value has to be between 0 and 100.");

        temp = 0;

    } else {

        temp = tolerance * (0xFF000000 | 0xFF000000) / 100;

    }

    final int toleranceRGB = Math.abs(temp);



    final ImageFilter filter = new RGBImageFilter() {

        // The color we are looking for (white)... Alpha bits are set to opaque

        public int markerRGBFrom = (color.getRGB() | 0xFF000000) - toleranceRGB;

        public int markerRGBTo = (color.getRGB() | 0xFF000000) + toleranceRGB;



        public final int filterRGB(final int x, final int y, final int rgb) {

            if ((rgb | 0xFF000000) >= markerRGBFrom && (rgb | 0xFF000000) <= markerRGBTo) {

                // Mark the alpha bits as zero - transparent

                return 0x00FFFFFF & rgb;

            } else {

                // Nothing to do

                return rgb;

            }

        }

    }; 

    final ImageProducer ip = new FilteredImageSource(im.getSource(), filter);

    return Toolkit.getDefaultToolkit().createImage(ip);
}

回答3:

Here is my solution. This filter will remove the background from any image as long as the background image color is in the top left corner.

private static class BackgroundFilter extends RGBImageFilter{

    boolean setUp = false;
    int bgColor;

    @Override
    public int filterRGB(int x, int y, int rgb) {
        int colorWOAlpha = rgb & 0xFFFFFF;
        if( ! setUp && x == 0 && y == 0 ){
            bgColor = colorWOAlpha;
            setUp = true;
        }
        else if( colorWOAlpha == bgColor )
            return colorWOAlpha;
        return rgb;
    }
}

Elsewhere...

ImageFilter bgFilter = new BackgroundFilter();
ImageProducer ip = new FilteredImageSource(image.getSource(), bgFilter);
image = Toolkit.getDefaultToolkit().createImage(ip);