Paletted / Indexed PNG as Textures, with <= 16 Colors, Fail

[joecks]

I described an issue in the bugtracker http://code.google.com/p/libgdx/issues/detail?id=895, where loading a PNG texture with less then 17 indexed colors is failing, 17+ colors works perfectly. Could that be related to the Pixmap Constructor JavaDoc entry, which says that "Paletted formats are not supported":

Code: Select all

/** Creates a new Pixmap instance from the given file. The file must be a Png, Jpeg or Bitmap. Paletted formats are not
    * supported.
    *
    * @param file the {@link FileHandle} */

So could I switch to the alternative constructor, which is taking a different offset, and so fix this issue?

Alternative Constructor:

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/** Creates a new Pixmap instance from the given encoded image data. The image can be encoded as JPEG, PNG or BMP.
    * @param encodedData the encoded image data
    * @param offset the offset
    * @param len the length */
   public Pixmap (byte[] encodedData, int offset, int len) {
      try {
         pixmap = new Gdx2DPixmap(encodedData, offset, len, 0);
      } catch (IOException e) {
         throw new GdxRuntimeException("Couldn't load pixmap from image data", e);
      }
   }

[mzechner]

We use stb_image for image loading. That library does not support indexed PNGs and due to that, neither can we. One solution would be to wrap libpng, but i'm afraid i lack the time to do that at the moment :/

[joecks]

Interesting. But how does that correspond to my observation with less then 17 Colors. Loading 17+ palatted / indexed PNGs works perfectly, below that number loading crashes!

[mzechner]

Good question, for that we'd have to look into stb_image's PNG decoder. To be frank, i have no idea why it would behave like this, the docs state that paletted PNGs aren't supported, so i'm puzzled that it returns anything for +16 color paletted PNGs.