PNG with transparent background turns black when resized with Scalr

Question

I am using org.imgscalr.Scalr(http://www.thebuzzmedia.com/software/imgscalr-java-image-scaling-library/#solve) libraries to resize the images but the PNG with transparent background turns black when resized. My code is as mentioned below:

    public void scaleImage(String originalImage, int width, int height) throws IOException {
    File imgFl = new File(originalImage);
    BufferedImage originalBufImage = ImageIO.read(imgFl);
    BufferedImage scaledImage = Scalr.resize(originalBufImage, Scalr.Method.ULTRA_QUALITY, width, height, Scalr.OP_BRIGHTER);
    File outputfile = new File(originalImage);
    String fileExtension = originalImage.substring(originalImage.indexOf(".") + 1, originalImage.length());
    ImageIO.write(scaledImage, fileExtension, outputfile);
}

Does anyone has any clue about this?

Thanks, Abhishek

Answer 1

I don't know why it happens, but assuming that nothing else is black in the image, you can make the black color transparent with this method:

private static Image mct(Image im, final Color color) {
    ImageFilter filter = new RGBImageFilter() {
      // the color we are looking for... Alpha bits are set to opaque
      public int markerRGB = color.getRGB() | 0xFF000000;

      public final int filterRGB(int x, int y, int rgb) {
        if ( ( rgb | 0xFF000000 ) == markerRGB ) {
          // Mark the alpha bits as zero - transparent
          return 0x00FFFFFF & rgb;
          }
        else {
          // nothing to do
          return rgb;
          }
        }
      };

It returns an image with all RGB values that match the color as transparent.

I hope this helped.

Answer 2

Scalr probably isn't using BufferedImage.TYPE_INT_ARGB when creating the new BufferedImage - perhaps you can ask it to?