Red shifted images when transcoding to JPG/PNG

1

We have a bunch of image formats we are interested in transcoding to PNG/JPG using the downloadable batch pvrtextool as an evaluation. There seems to be a number of cases where images are red shifted, and this seems to have little to do with the actual PNG/JPG - if we convert from TGA (say) to DDS or PVR, and then using the DDS (say) to convert to PNG, the red shift is present.

This occurs even if we have a greyscale image - loading into gimp, say, shows the colours to be white and red, not black.

For some test high resolution images, the effect can be completely unnoticable by eye, but a difference comparison of the output image with another conversion tool can show a speckling of red over the pvr converted image.

Any assistance you can give in the matter would be gratefully received,
Many thanks,
Antony

2

Hi Antony,

Welcome to the PVR Developer forum and thank you for reporting the issue with PVRTexTool. We are discussing this behaviour with our tools team and shall get back to you soon once we have more information. Thank you for your patience.

Regards,
Nagnath

3

Hi Antony,

Could you please share the following information to better understand the issue you are facing,

  1. PVRTexTool version
  2. By image formats do you mean texture formats or image file formats (containers). And the formats you are trying to transcode between?
  3. some test images to reproduce the issue at our end

Thanks,
Nagnath

4

Hi Nagnath,

Many thanks for getting back to me.

We are using the 2021_r1 download, which identifies itself:
    PVRTexToolCL v5.1 (PowerVR SDK 21.1@5986312)

Conversion is simply specified:
   pvrtextool -i <input tga file> -o <any pvr or dds save file> -d <output jpeg file>

Note that if we perform this as a two stage process, -i tga -o dds/pvr, and then -i dds/pvr -d jpeg the result is the same. It appears it is doing the same red shift for png conversion, and the error is in the dds/pvr

I tried to upload samples, but it says new users are not authorised to do so,

Antony
5

Hi Antony,

Thanks for getting back with the details. Could you please test it with the PVRTexToolCLI v5.3.0 ( PowerVR SDK 22.1 ) which could be downloaded from here
Sorry to know that you were unable to upload files here. For us to be better support you on your issue, kindly register and raise a ticket in our support portal, [PowerVR Insider Support] [https://pvrsupport.imgtec.com] (https://pvrsupport.imgtec.com/)

Best Regards,
Nagnath