# How to compress JPG without alpha channel with the ASTC

**URL:** <https://forums.imgtec.com/t/how-to-compress-jpg-without-alpha-channel-with-the-astc/3491>\
**Category:** Uncategorized\
**Tags:** pvrtextool\
**Created:** [January 14, 2022, 2:27am UTC](https://forums.imgtec.com/t/how-to-compress-jpg-without-alpha-channel-with-the-astc/3491 "2022-01-14T02:27:12Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![simonastcask](https://avatars.discourse-cdn.com/v4/letter/s/71c47a/32.png) [@simonastcask](https://forums.imgtec.com/u/simonastcask)\
**Post date:** [January 14, 2022, 2:27am UTC](https://forums.imgtec.com/t/how-to-compress-jpg-without-alpha-channel-with-the-astc/3491/1 "2022-01-14T02:27:12Z")

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i find out that the jpg with a alpha channel after compressed with astc

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**Author:** ![AlejandroC](https://avatars.discourse-cdn.com/v4/letter/a/97f17d/32.png) [@AlejandroC](https://forums.imgtec.com/u/AlejandroC)\
**Post date:** [January 17, 2022, 11:51am UTC](https://forums.imgtec.com/t/how-to-compress-jpg-without-alpha-channel-with-the-astc/3491/2 "2022-01-17T11:51:29Z")

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Hi simonastcask,

Correct me if I am wrong, but if I understood correctly, you want to know how to compress a jpg file with no alpha channel to ASTC, with the final compressed ASTC file having alpha channel?

If that is the case, you can do it with PVRTexToolCLI:

> PVRTexToolCLI -i test.jpg -f ASTC\_4X4 -q astcveryfast -o test.ktx

Remember that in the current version of PVRTexToolCLI, you need to use a block size for ASTC that is an integer factor of the image dimensions. For instance, if you have an image with dimensions 640x800, you cannot use ASTC\_6X6 since 640/6 = 106. **67** and 800/6 = 133. **33**. Instead, you can use ASTC\_4X4, since 640/4=160. **0** and 800/4=200. **0**

Best regards,  
Alejandro