No ImageMagick? No problem, use FFmpeg!

Ok this is clickbait, but hear me out.

The alternative to imagemagick for simple scaling, rotation and image conversion actually works.

And I’ll explain why I didn’t/couldn’t go with ImageMagick (on my Kindle), which would be my go-to tool.

–

I rooted my Kindle.

The shell is very limited.

The Kindle runs on

Linux kindle 3.0.35-lab126 #8 PREEMPT Fri Sep 13 12:49:59 UTC 2024 armv7l GNU/Linux

I don’t have a package manager, I could install Alpine on it and get apk but couldn’t get it to work after enough fiddling, and I actually didn’t need it turns out.

I wanted to display an image from my Tapo camera, but it doesn’t have a snapshot endpoint, only an RTSP stream.

So here comes FFmpeg to the rescue.

Here is the command I needed to get the image from the stream, and more importantly resize it, convert to gray-scale 8-bit PNG and rotate it:

ffmpeg -i "rtsp://<username>:<password>@<ip>:554/stream1"
-f image2 # stores sequence of individual image frames as separate files
-pix_fmt gray # convert to grayscale, 8bit PNG
-vf "scale=1920:-1,transpose=1" # scale it, maintain aspect ratio, and rotate by 90degrees clockwise
-vframes 1 # I just need 1 frame
output.png

I hear you shouting at the screen “BUT I DON’T HAVE A STREAM, I JUST HAVE AN IMAGE!”

Simply replace the stream url with your local image.

Here is a link to the FFmpeg docs about its filters