Pass stdin to stdout if optimization was not possible

[KrylosovM]

cat a.jpg | jpegoptim --stdin > b.jpg

Would be great if input file from stdin passed to stdout when result of optimization is larger than original.
At the moment --stdin option enables --force option that forces optimized file to stdout, even if it is larger than original.

[Lewiscowles1986]

I Just got this same thing trying to make this into a serverless function.

https://github.com/Lewiscowles1986/func_jpegoptim

[Lewiscowles1986]

going to try this out with a build.

• https://github.com/tjko/jpegoptim/blob/master/jpegoptim.c#L468
  seems to be the place to go to start
• https://github.com/tjko/jpegoptim/blob/master/jpegoptim.c#L469
  could benefit from enforcing quiet for my purposes (otherwise my serverless function outputs noise that outputs an invalid jpeg
• https://github.com/tjko/jpegoptim/blob/master/jpegoptim.c#L808
  Add additional checks (probably borrowed from elsewhere)

[Lewiscowles1986]

Right I've a patch for this. It was a bit more of a pain than I first thought, but it now works on my PC and I'm pretty happy

[Lewiscowles1986]

@KrylosovM @tjko
My solution would likely benefit from feedback. I've made a heap of assumptions, but I feel pretty positive about it.

The latest commit adds a command line argument for --read-bytes shortcode -B which takes the number of bytes passed to stdin. It also checks that is larger than the minimum possible size for a valid JPEG, and detects if the input to stdin is larger than the buffer (defaults to 32MB).

It does change the behaviour so that -f is not passed by default and that output is silenced when --stdin or --stdout arguments are provided.

[tjko]

This has now been implemented with commit: 05c3f85