I Finally Fixed ChatGPT Image Ratio with Stable Diffusion Outpainting
One thing that kept bugging me:
ChatGPT’s image-1 model doesn’t support common aspect ratios like 16:9 or 9:16, which is kind of a problem when you’re making YouTube thumbnails or Shorts.

As the founder of AIThumbnail.so, I really wanted users to get clean, crisp 1920x1080 thumbnails without messing around with weird crops, white padding, or manual resizing.
So I built a fix.
Here’s the little workflow I came up with, it combines smart stretching + outpainting (using Stable Diffusion) to get perfect 16:9 images:
🛠️ How it works:
✅ Takes the original image from ChatGPT
✅ Stretches it (only slightly, no weird distortion)
✅ Figures out what pixels are still missing
✅ Uses Stable Diffusion to outpaint and fill the edges
✅ Outputs a clean 1920x1080 image, no loss, no borders, no fuss
Why this matters:
If you're working with AI-generated images, you’ve probably run into the same issue:
Cropping ruins important parts of the image
Padding looks bad or amateur
Wrong aspect ratios kill your flow on YouTube, Shorts, etc.
The result: Now every image on AIThumbnail.so is auto-fixed and ready to use, no editing needed.
If you're working on anything similar or want to automate this kind of fix, feel free to ask,
happy to share how I set it up.
Thanks for reading!
Replies
I generate lots of images for my gaming content, and it’s always a pain resizing them to 1920x1080. This workflow is exactly what I needed but didn’t know I needed.
AIThumbnail.so
@kathe_jordan great to hear! do you have a youtube channel?
Haye
I'm not sure if it's possible to enforce this through prompts. We recently designed a new feature that requires configuration when users generate images, but I'm not sure if the effect is as expected
AIThumbnail.so
@hi_caicai it is pretty good so far! likely give it a shot.
This is clutch. I’ve wasted way too much time resizing and praying stuff doesn’t get cropped weird. Would love to peek under the hood—how are you keeping the outpainting consistent with the original style?
AIThumbnail.so
@pravin_meh66451 I currently use this prompt:
"Extend the current image to fit a 16:9 aspect ratio by blending the existing background seamlessly. Do not introduce any new elements or objects. Keep the lighting, textures, and color palette consistent. Prioritize minimalism and natural background extension only. Avoid adding text, logos, people, or any focal point changes."
It is pretty much perfect 90% of the time. Then a few time i manually use my "magic erasor" to smooth some area
IndieCrush
finally ! thx bro
AIThumbnail.so
@alexsssaint thanks!! do you think It is useful enough to be a mini tool on its own?
IndieCrush