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POJava: Generating thumbnails with transparency
 

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  1. POJava: Generating thumbnails with transparency
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    <p>I'm having problems generating thumbnails of images with an Alpha channel (transparency). The code I use is this:</p> <pre><code>public void saveThumbnail(File file, String imageType) { if (bufferedThumb == null) { return; } if(bufferedImage.getColorModel().hasAlpha()) { logger.debug("Original image has Alpha channel"); } BufferedImage bi = new BufferedImage(bufferedThumb.getWidth(null), bufferedThumb.getHeight(null), BufferedImage.TYPE_INT_ARGB); Graphics g = bi.getGraphics(); g.drawImage(bufferedThumb, 0, 0, null); try { ImageIO.write(bi, imageType, file); } catch (IOException ioe) { ioe.printStackTrace(); System.out.println("Error occured saving thumbnail"); } } </code></pre> <p>However, if I supply for example a GIF image with a transparent background I always end up with a black or colored background.</p> <p>EDIT:</p> <p>This is how it's called from the class using the thumbnail, I missed the two-parameter version of the getThuimbnail()-method the last time:</p> <pre><code>Thumbnail th = new Thumbnail(file.getPath()); th.getThumbnail(100); </code></pre> <p>Added methods used for getting the images:</p> <pre><code>public Thumbnail(String fileName) { try { this.bufferedImage = ImageIO.read(new File(fileName)); } catch (IOException ex) { logger.error("Failed to read image file: " + ex.getMessage()); } } public Image getThumbnail(int size) { int dir = VERTICAL; if (bufferedImage.getHeight() &lt; bufferedImage.getWidth()) { dir = HORIZONTAL; } return getThumbnail(size, dir); } /** * Creates image with specifed max sized to a specified direction. * Will use Image.SCALE_SMOOTH for scaling. * @param size Maximum size * @param dir Direction of maximum size - 0 = vertical, 1 = height. * @return Resized image. */ public Image getThumbnail(int size, int dir) { return getThumbnail(size, dir, Image.SCALE_SMOOTH); } /** * Creates image with specified size. * @param size Maximum size * @param dir Direction of maximum size - 0 = vertical, 1 = height. * @param scale Image.Scale to use for conversion. * @return Resized image. */ public Image getThumbnail(int size, int dir, int scale) { if (dir == HORIZONTAL) { bufferedThumb = bufferedImage.getScaledInstance(size, -1, scale); } else { bufferedThumb = bufferedImage.getScaledInstance(-1, size, scale); } return bufferedThumb; } </code></pre> <p>Thanks!</p>
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    1. COGIF images don't have an alpha channel, just a color marked as transparent. When you scale it down, you end up with data that can't be expressed as a GIF.
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      1. USJosh Lee
    2. COI see, so I would be better of always saving the thumbnail as JPEG or PNG?
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      1. USMalakim
    3. COWould be better using PNG. Perfect for transparency.
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      1. POJava: Generating thumbnails with transparency
      1. USGordon
 

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