Color difference

[wzq9]

Hi, I am converting jpg or png to ktx2 which has been provided for my model to use, and the following problem occurs when I use compression
This is the command I used
ktx create --generate-mipmap --encode basis-lz --qlevel 255 --assign-tf srgb --assign-primaries bt709 --format R8G8B8_SRGB --threads 2 ./Map614327993.jpg ./Map614327993.ktx2
toktx --lower_left_maps_to_s0t0 --encode etc1s ./Map614327993.ktx2 ./Map614327993.jpg

There is a noticeable color difference, what do I need to fix this
jpgORktx2.zip

[MarkCallow]

What are the left and right images? It is not clear because you have shown 2 different ktx commands.

Note that the .jpg loader is not officially supported and does not support the full panoply of .jpg images. It is used by both ktx create and toktx and assumes the images are sRGB so you do not need to use --assign-tf. Both commands will create R8G8B8_SRGB format textures. You need to make sure your graphics pipeline is handling the sRGB textures correctly. It is preferable to use an sRGB framebuffer as conversion from 8-bit sRGB to 8-bit linear is potentially lossy dependent on the image content.

[wzq9]

Ok, let me add that the image on the left is jpg and the image on the right is ktx2 opened with NVIDIA Texture Tools Exporte which is from the first command, and of course the second command is the same phenomenon

Then I converted jpg to png and the same phenomenon occurred

So I can understand that the transformation loss, the repair is to use uastc (because uastc is running out correctly)

[MarkCallow]

Are you saying the converted png image showed the same phenomenon or that using the converted png image as input to ktx create showed the same phenomenon? If the former, how did you convert the jpg to png?

[wzq9]

Ok, I used some online tools to convert jpg to png and here's the picture
Then I convert to ktx2 with the first and second commands, respectively

From left to right, png is ktx2 from the first command and ktx2 from the second command