This conversation has been merged. Please reference the main conversation: Photoshop: Export As is adding extra canvas space.
A disturbingly majority of the time, when exporting an image, it will disregard canvas bounds. Sometimes this will mean including areas outside the canvas, if pixels exist outside and have not been cropped and deleted - which is not always convenient (say if you are wanting a large background image that you may wish to move to create other media, and not permanently crop).
Often these are only 1px wide, and aren't noticeable in thumbnails, so you think the file had exported correctly, and you check it, and in windows photo viewer it's framed on black so if your image has a white background, like 90% of product images, you can't see it, until it gets uploaded to the client website on a white background and there's suddenly a GLARING line on one edge or partly on one edge of a picture.Putting a white fill around the edge does not fix the issue - as it's adding pixels outside the canvas bounds. The only workaround is to increase the canvas bounds, add white, and then re-crop the image. This is unacceptable - the exporter should export the canvas area, and the canvas area alone.
When exporting to specific sizes, it will randomly fail to export to the requested size, demanding '599px' instead of '600px', for example. Save for web never had this issue, and still doesn't.
I suspect the two issues are related - and I suspect it may have something to do with the calculations not using long/floating point precision so that the calculations are flawed.
The exporter is broken, and has been since it was introduced.