Skip to main content
Convertly supports AI parameters on the same CDN URL. Forma-backed transforms (upscale, background replace, object removal, generative fill, text-to-image) bill against your workspace Forma AI quota and require a Pro plan or above. ML background removal is available on all plans and does not consume Forma quota.
Doc examples for bgRemove are generated against production CDN when rembg is deployed on Railway. If the CDN returns 502, the generator falls back to local ML — edge quality may differ from production.
Product with background removed on a styled canvas
Background removal before and after
Product on replaced studio background
AI generated product hero image
Object removal before and after

​
Parameters

ParamValueQuota
bgRemove (bg-remove)1, true, yes, or on — ML background removal with alpha.None
upscale1, true, yes, or on — Forma super-resolution (see limits). Optional 2 or 4 to cap the factor.Forma AI
bgReplace (bg-replace)URL-encoded scene prompt. Keeps the subject, replaces the background.Forma AI
objectRemovalRect (object-removal-rect)Region to remove: x,y,w,h in source pixels or percentages. Optional objectRemovalPrompt.Forma AI
fill=gen + fillGenPromptGenerative outpaint. Add fillPad=120 or per-side fillExpandTop / Right / Bottom / Left.Forma AI
ai=generate + aiPromptText-to-image. Optional ar=16:9 for aspect ratio. Ignores the source file bytes.Forma AI
Signed URLs required: upscale, bgReplace, objectRemovalRect, fill=gen, and ai=generate must use an HMAC-signed URL (s= + optional exp=) so premium transforms cannot be tampered with in transit. bgRemove works on unsigned public URLs. 
<!-- ML background removal (no Forma quota) -->
<img src="https://cdn.convertly.sh/{key}/{id}?bgRemove=1&format=webp" />

<!-- Forma super-resolution (signed URL + quota) -->
<img src="https://cdn.convertly.sh/{key}/{id}?upscale=1&w=1600&s=…&exp=…&format=webp" />

<!-- Forma background replacement (signed URL + quota) -->
<img src="https://cdn.convertly.sh/{key}/{id}?bgReplace=sunset%20beach&s=…&exp=…&w=800&format=webp" />

<!-- Object removal in a source region -->
<img src="https://cdn.convertly.sh/{key}/{id}?objectRemovalRect=120,80,200,160&s=…&w=1200" />

<!-- Generative fill / outpaint -->
<img src="https://cdn.convertly.sh/{key}/{id}?fill=gen&fillGenPrompt=extend%20the%20forest&fillPad=200&s=…&w=1200" />
Forma transforms run on the source image first, then sizing, crop, and encode params apply. Use bgRemove=1 alone when you need a transparent PNG cutout. Use bgReplace=… when you want a new scene — Forma keeps the subject and replaces the background in one step.

​
Super-resolution (upscale)

Forma super-resolution increases detail on the source image before w, h, crop, and format params run.
Super-resolution before and after
Resize-only upscale comparison
Forma super-resolution result
Use upscale=1 when you need recovered detail, not just larger pixels. Requesting a larger w or h without upscale only interpolates existing pixels (similar to a standard resize).

​
Super-resolution limits

Convertly enforces these input limits on AI transforms:
Longest source edgeMaximum upscale factor
Under 2048 pxUp to 4×
2048–4096 pxUp to 2×
Over 4096 pxNo upscale (resize params still apply)
Generative upscaling improves detail but cannot fully recover illegible text or heavily corrupted sources. For the clearest before/after in your own assets, start from a moderately small source (roughly 320–800 px on the long edge).

​
Tips

  • Difficult cutouts (contact shadows, glass, fine hair): try bgReplace=… first. If you still need a standalone transparent asset, use bgRemove=1 on a separate URL.
  • Heavy Forma load: the CDN may return 423 Locked with Retry-After: 30. Retry the same signed URL; successful responses are cached at the edge.
  • Studio/API access: the same Forma operations are available via Forma AI in the editor and POST /api/ai/transform.