Exporting images at different scales causes white pixel gaps

[aaaaaaaaaa0]

Version: 23.1.1

My images are 1366 x 768. Exporting at 0.75x scale causes their width to round up to 1025px, which adds an single white pixel gap at the edge of the exported images. Instead of normal rounding, this calculation should round down to the nearest integer (floor) to prevent the white gaps.

-I've tried changing the image and canvas size to 1024px, and exporting at 1x scale

-I've tried increasing the artboard sizes by 1px (1367), and then doing the same

These workarounds change the results slightly, but do not fix the underlying problem

- I Can't even export with legacy since it ignores artboards

[BrettN]

1366 x .75 = 1024.5. We will definitely round up on such math. We also generally err on the side of keeping/generating new information rather than cutting/losing information.

While I do get a slight lightening of edge pixels (only visible when zooming in all the way), I haven't gotten a noticbly white line from my testing. I'm guessing there is something about the content of your file which is making this happen. Would you be able to share the file so I could take a look? 

[aaaaaaaaaa0]

Using the exact same file I originally had this issue with, it seems to have been adressed in 23.2, or else something changed on my end since then. I will reply to this thread if it comes up agian. Cheers!

[BrettN]

We had a number of fixes with the latest update, so it is good to hear that this may have been addressed.

[stevetb77]

I believe I'm having this issue using Export As with an artboard when using the Scale All feature.  Depending on the scale I choose, some of the images from the artboard get a white line / lines on the top, the bottom, or the top or bottom and left or right side.  This white line can be multiple pixels thick.
If I resize the artboard first and then Export As with 1x (normal) scale this does not happen.  I think there is a bug with the scale all feature.

[stevetb77]

It appears I have this issue sometimes even when resizing the artboard, the difference is I can fix each one manually before export.  This issue is surprising.

[BrettN]

  I see the behavior you are talking about. Unfortunately I'd have to say it is expected and I'll explain why. Whenever you increase the size of a document you are creating new pixels. To determine what color those pixels are you have to compare the pixels surrounding them (interpolation). The pixels at the edge of the document may behave differently depending on how the document treats that edge.

  If your document is flattened (just a background layer) there is no information beyond the edge of the canvas, so it doesn't contribute to interpolation and you get edge pixels that are more or less what you might exect. 

  If you have an artboard or you otherwise have no background layer, the area outside the canvas bounds is considered to be an infinite array of transparent pixels. These transparent pixels beyond the edge are taken into consideration with interpolation. When you combine transparency with a solid color pixel, you end up with a lighter pixel, which gives the edge pixels a whiter appearance. You'll even see this without artboards if you take a flattened image, convert the background to a normal layer, and then Export As.

  The way to avoid this is to give your document a bleed. That is, if you have some sort of pixel information beyond the edge of the canvas which will be used for interpolation instead of transparency. It can be as little as 1 pixel around the edge of your image. For testing purposes, I merely transformed my layer so that it was an extra pixel wider in all directions before exporting. You could do any number of things to give youself this bleed on your artboard and then it will remove the lightness of your edge pixels. 

[Stephen Marsh]

@BrettN – thank you for the explanation, I have marked this as a correct answer.

[stevetb77]

Thank you for the thoughtful response.  Is this the same for scaling down?  I'm scaling down to .33x or .25x.  I'm not just getting a lighter line, I'm getting a white line.  I don't see how this could really be expected behavior as I'm just a regular user and I totally do not expect this behavior.  Even if you can logically explain why it is occuring, that does not mean it should occur (in my opinion).  If I have an image inside of an artboard and I use export as and "Scale All", I'm expecting the output to be a scaled version of my original without strange artifacts like solid white lines.  For that reason I would call this a bug. 
I believe I tried your solution without success.
I added a black backround to each artboard and made it significantly larger on all sides than each artboard.  
I still got a solid white line on export. 
I stretched the main images in the artboards beyond the edges on all sides and tried it, still got the white lines.
Here's an example, a solid blue rectangle exported with Export As, Scale All .33X.
For this I had a solid black layer below this stretched beyond the bounds of the artboard on all sides.
Thank you, much appreciated!

[Stephen Marsh]

Try making the blue larger than all four sides of the artboard.

[stevetb77]

I did exactly that, the output was identical to what I shared - white line on top

[Stephen Marsh]

I did exactly that, the output was identical to what I shared - white line on top

By @stevetb77

OK, because you wrote:

"For this I had a solid black layer below this stretched beyond the bounds of the artboard on all sides."

Which I read as being separate and different to the content in the artboard itselft.

I tried to reproduce this but couldn't in either 22.5.9 or 25.9.1.

Can you share a sample .psd file that exhibits this behaviour?

[stevetb77]

Yes, I tried a black layer stretched beyond the bounds of the artboard underneath the main content.  That didn't work, then I tried stretching the main content beyond the bounds, that didn't work.
I'm using 25.11.0 beta.
I simplified the project to two artboards.
If I export "Export As", "Scale All" at .33X scale, Block 2 has the white line on top.
Curious if this happens for you as well.
This is a problem because I have to do A LOT of this and I want to automate it, this issue is in my way big time.
Thanks!

[Stephen Marsh]

@stevetb77 

I can reproduce your issue in 25.9.1 (Ps 2024) with the Export As from each artboard.

When viewing the artboards at different reduced zoom levels, one would think that the error is to be found at the bottom of the exported image.

Here the blue background is exactly the same size as the Block 2 artboard, however at reduced zoom levels a transparent gap appears onscreen due to zoom rounding at less than 100% (1:1 view). But why for the second artboard and not the first?

Here I have extended the blue background, as one can see by the transform bounding box on Block 2:

However, the gap in the 0.33% export is produced at the top of the image, not the bottom (viewed at 100%):

I too would call this a bug.

[stevetb77]

Excellent (that you were able to reproduce the issue)!
How do we report this?
Thanks!
 

[Stephen Marsh]

It was posted as a discussion and not as a bug. I'll use the report link to ask a moderator to change the label.

[cannon303]

The bleed idea doesn't work for me. I have a lot of pixels beyond the edge of the canvas and I still get the white lines. I'm exporting at full size and 0.33x preset and it's the 0.33x preset where I see the white line.  I've never got on with this latest export feature in Photoshop and it still has no WebP support. It needs a rethink.