Extracting/Transcoding single images from blockfile of images

[phipno]

Hello,
If you compress multiple images at once via the m_source_images vector, can you extract each compressed image separately afterwards and if yes, how so?

I figured you need to transcode again, but getting those images extracted, I struggle with.
I used the ktx2_transcoder and basisu_transcoder transcode_image_level() function to try this, but it never gave the hoped for output. The output should be ETC1 with an ktx2 container.

I want to do the "blockcompression" because with OpenCL enabled, I hope for a big speed up in the compression time compared to calling basisu processor, jpool and creating params for each image.

Is there something I'm missing?