FPReaderPNG doesnt read 16bit Gray (single channel) PNG files

[CorBee]

Hi,

I am developing an application where I need to be able to read 16bit single channel gray PNG images. The FPReaderPNG does allow me to read the images but the data that I get from the images is only the upper 8 bits of the 16bit data. Other 16bit PNG files do work as planned.

Anybody with an idea where to fix this ?

kind regards
CorBee
*************************************************
RegiStax Free Image Processing Software
http://www.astronomie.be/registax
*************************************************

[Timewarp]

http://bugs.freepascal.org/view.php?id=24382

[CorBee]

Thanks. So an unresolved issue ..

[Timewarp]

So an unresolved issue ..

And expected to remain (unless someone commits the patch)

BGRABitmap has this fix included.

[CorBee]

In BGRABitmap I see this routine
function TBGRAReaderPNG.ColorGray16 (const CD:TColorDAta) : TFPColor;
var c : NativeUint;
begin
  c := CD and $FFFF;
  with result do
    begin
    red := c;
    green := c;
    blue := c;
    alpha := alphaOpaque;
    end;
end;

Thats no different from the routine in FPreadPNG.

[Timewarp]

Problem is in ColorGrayAlpha16
Are you sure your images don't have alpha?
 

[CorBee]

Unfortunately I cant access the part where the FPreadPNG gets the info on the format. That info is not accessible during the loading in Lazarus.

[CorBee]

Ive switched to the Vampyre Imaging Library ... turns out that the file was Gray16 without alpha.

regards
Cor

[Timewarp]

Can you attach sample png?

[CorBee]

The images are 3Mb in size, does the forum allow that ?

[circular]

You can put a link to Dropbox, GoogleDoc...

[CorBee]

Try this
https://www.wetransfer.com/downloads/f9f99e5cdf9197bf23475a8fc7c152a620141122134233/1e0194152a26ae3aeef98d95232f05e320141122134233/cd666b

or

http://we.tl/sifb0a2dU3

[marcov]

So an unresolved issue ..

And expected to remain (unless someone commits the patch)

BGRABitmap has this fix included.

It has been waiting for sb to do a thorough investigation for some time now.

[circular]

The image seems to load well with BGRABitmap. It is 16-bit grayscale without alpha.

[CorBee]

Good to hear that, I am using the Vampyre library currently. It would be nice to have a library that can read all the 16bit formats