Can I make JPEG exports preserve all colors?

[bjf]

Hi, I'm a long-time user of PDN, but apparently I still have questions about it... I searched previous posts on here and on Google, and had trouble getting a straight answer.

 

The Problem

I am working with a source image that is in PNG format. This image contains a color with the hex code #796F75. Because I must export as JPEG, I am keeping the alpha at 255. Upon saving the image as a JPEG (even with Quality=100, Chroma Subsampling=4:4:4) and reopening the image in PDN, this color has magically transformed itself to #7A6F75. I attached a 16x16 PNG of nothing but #796F75 if you'd like to download and try.

 

Color Profiles?
I see this term come up a lot when Googling around this issue, but I'm not really sure what it has to do with this problem. I found a post on this forum from 2012 that says PDN had no concept of color profiles, and as far as I can tell, sRGB and YCbCr both handle full 24 bit-depth of colors anyways.

 

My Question

Is there a setting I'm missing in PDN, a missing feature, a problem with JPEG, or something else entirely? Is it possible for me to save a JPEG with this exact color?

 

Thanks,

Brandon

 

Edit 1: I'm using paint.net v4.2.12

Edited June 16, 2020 by bjf

[BoltBait]

JPG is a "lossy" format, even at 100%.  There really is no way to do what you want.  Why are you forced to export in JPG format?

[bjf]

Facebook seems to always perform a conversion to a JPEG if I upload as PNG.

[BoltBait]

Yes, and they compress the hell out of everything.  So, even if you upload a JPG at 100%, don't count on it being the same file as you upload.

 

Trying to get exact colors on FB is a lost cause.

[bjf]

True, but does compressing even a 16x16 single-color image mean that the original color value can't be preserved? And regardless of whether or not Facebook modifies the image, is it impossible for this image to exist on my hard drive?

Edited June 16, 2020 by bjf
Update my question

[BoltBait]

Due to the nature of JPG images, some pixel colors are changed (sometimes more than) slightly so that the image compresses better.  Apparently #7A6F75 compresses better than #796F75.  (I have no idea why.)

 

So, if your original intent was to have #7A6F75, then you would have been in luck.  As it is, you want #796F75... so, you are out of luck as it will be changed in order to compress better.  JPG is not good for getting very specific colors.  For that, you should try a lossless format, like PNG. 

 

You could try a palettized format, like GIF... I wonder if FB would accept a GIF file and keep it that format.

[bjf]

It was worth a try, though it doesn't seem like Facebook likes static GIFs right now. Anyways, it sounds like this isn't a paint.net issue, so I'll keep this discussion from going off-topic any further. It sounds like to solve my problem, I'll need to get a better understanding of JPEG compression algorithms to see if I can avoid this issue in the future. For now, thanks for your help!

[BoltBait]

I tried...