Just for some insight:
I was trying to optimise file size by using a 4 bit palette and this was a
suitable and simple way of doing so.
Another tip I found was to avoid the use of anti-aliasing, because it ends up
generating intermediate colours, which makes PNG compression more difficult
even though the palette bit-depth hasn't changed.
When testing with native JAI and I/O, I found that when using a non-standard
case, Sun/Oracle don't seem to bother optimising. Judging by the file sizes,
they fall back to non-native.
Simon
.
From: [email protected] [mailto:[email protected]] On Behalf Of Andrea
Aime
Sent: 29 November 2013 11:16
To: Simon Hartley
Cc: Geoserver-devel
Subject: Re: [Geoserver-devel] New PNG encoder: how about a GSIP to merge it
into core on trunk?
On Fri, Nov 29, 2013 at 12:06 PM, Simon Hartley
<[email protected]<mailto:[email protected]>> wrote:
When playing with the code I created a 4 bit grayscale image.
The reason I use ushort is because it results in better quality images than if
I use byte (I had issues with lines not drawing smoothly).
BufferedImage bi = ImageTypeSpecifier
.createGrayscale(4,
DataBuffer.TYPE_USHORT, false)
.createBufferedImage(width,
height);
The ScanlineProviderFactory didn't like this because of the use of USHORT in
combination with an IndexColorModel.
One thing I needed to do to get it to work is create a constructor on
RasterShortSingleBandProvider which takes a bit depth (4 in this case).
Weird setup indeed. Yes, what you propose should work.
More in general, this PNG encoder should probably have a fallback mode, if we
cannot create a scanline provider,
it should fall back on the JDK one I guess, to make sure it does not break when
plugging custom raster sources
like yours.
Looking at the code, can the final <else if> ever work?
The previous <else if> checks if the ColorModel is an instance of
IndexColorModel and then the next <else if>,
knowing that it isn't an IndexColorModel, casts the ColorModel to
IndexColorModel.
No, you're right, it does not. Weird, I guess none of the official PNG color
models ever get there
Cheers
Andrea
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