Photoshop 19.1: JPEG exportation with scaling produces different results

I can't duplicate the issue using PS 9.1.0. Please provide screenshots showing the original image and two PS version renderings.

Ok, here goes:

Source (2048):


JPEG export (1024) - Photoshop 2017:


JPEG export (1024) - Photoshop 19.1.0:

I looked at an image similar to yours and there is a 1 pixel shift, but in the left to right direction. I think what you are seeing is due to the interpolation method used. Bicubic and Bilinear sample the surrounding pixels to come up with the new pixels. Dependind on the image it could easily shift it by 1 pixel. Try using Nearest Neighbor in the Save As Resample setting. On my image it doesn't create any visible shift, but it can create stair-step artifacts.

No, see original post.  It's not the method used.  We used the same exact method in 2017 and it did not cause this.  Furthermore, we went through every single interpolation option and they all produced the same result.

So how does this all work?  Does Adobe actually check these posts?  Because as far as I can tell there's no way to file tickets or speak to a live human being over there :\.

Yes Adobe Engineering does monitor these posts. I can't duplicate your exact 1 pixel down shift using my own image files. I suggest uploading an original PSD file that exhibits the issue along with Export As 50% Scaled JEPG files from PS 2017 and the latest PS version 19.1.0 to Dropbox. Provide the links here and I'll investigate further. Please also provide a screenshot of the 'Export As' settings window so I can use your exact settings.

In the interim you can try resetting the PS Preferences file to see if that corrects the issue. Close PS and then rename the Adobe Photoshop CC 2018 Prefs.psp with a .OLD extension as below. This will allow restoring it if the issue persists. When PS is launched a new Preferences file will be created with the default settings. Don't change any of its settings, but do try the Save As Export again and see if the results change.

Adobe Photoshop CC 2018 Prefs.psp.OLD

WINDOWS
Users\USERNAME\AppData\Roaming\Adobe\Adobe Photoshop CC 2018\Adobe Photoshop CC 2018 Settings\Adobe Photoshop CC 2018 Prefs.psp

MAC
Users/USERNAME/Library/Preferences/Adobe Photoshop CC 2018 Settings\Adobe Photoshop CC 2018 Prefs.psp

If no change repeat the above with your PS 2017 Preferences file and repeat the same test with PS 2017 to see if the results change.