Flux 2 Pro

Flux 2 Pro (black-forest-labs/flux-2-pro) is Black Forest Labs’ flagship for image generation. It works with two endpoints: POST /v1/images/generations for text-to-image and POST /v1/images/edits for working from a reference image. The model is paid — generations are charged from your balance.

Parameters

Field	Description
model	black-forest-labs/flux-2-pro (or the short flux-2-pro)
prompt	What to draw, required
n	How many images, 1 to 4; each one is billed separately
aspect_ratio	1:1, 2:3, 3:2, 9:16, 9:21, 16:9, 21:9; defaults to 1:1
resolution	1k or 2k; defaults to 1k
size	Explicit WxH — an alternative to the aspect_ratio + resolution pair
quality	The model has no such knob: passing the parameter returns 400

The model thinks in “aspect ratio + resolution” terms, and WxH is derived from them: 1k yields roughly a megapixel of area, 2k — roughly four. Mappings for common combinations:

Aspect	1k	2k
1:1	1024x1024	2048x2048
16:9	1344x768	2688x1520
9:16	768x1344	1520x2688
21:9	1568x672	3072x1296
9:21	672x1568	1296x3072

The full list of 14 allowed size values is the sizes field in the catalog; a value outside the list returns 400.

Examples

Text-to-image

Python

import base64

img = client.images.generate(
    model="black-forest-labs/flux-2-pro",
    prompt="Sneaker design concept on a last, studio light, clean background",
    extra_body={"aspect_ratio": "3:2", "resolution": "2k"},
)
with open("sneaker.png", "wb") as f:
    f.write(base64.b64decode(img.data[0].b64_json))

cURL

curl https://api.mixen.ai/v1/images/generations \
  -H "Authorization: Bearer $MIXEN_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "black-forest-labs/flux-2-pro",
    "prompt": "Sneaker design concept on a last, studio light, clean background",
    "aspect_ratio": "3:2",
    "resolution": "2k"
  }'

A wide banner with an explicit size

{
  "model": "black-forest-labs/flux-2-pro",
  "prompt": "Roastery banner: morning light, coffee beans, craft typography",
  "size": "3072x1296"
}

Editing from a reference

The model accepts reference images (references: true), so /v1/images/edits with multipart/form-data is available:

curl https://api.mixen.ai/v1/images/edits \
  -H "Authorization: Bearer $MIXEN_API_KEY" \
  -F model=black-forest-labs/flux-2-pro \
  -F image=@sketch.png \
  -F prompt="Turn the sketch into a photoreal render, keep the studio background"

The answer always carries b64_json — files are not hosted. Both endpoints answer synchronously; set your HTTP client timeout to at least 120 seconds.

Price

4.0108 ₽ ($0.045) per image — the flat catalog price. Current values — catalog.

Strengths and limits

• Seven frame formats, including the ultra-wide 21:9 and 9:21 for banners and covers.
• Two resolutions: 1k (about a megapixel) and 2k (about four, up to 3072x1296).
• Fourteen fixed size values — one per “aspect + resolution” pair.
• Editing from a reference via /v1/images/edits — the same key and syntax as generation.
• Nearby in the catalog: Flux 2 Flex at 8.0216 ₽ ($0.09) and Flux 2 Max at 9.3585 ₽ ($0.105) per image; the family shares the same parameter set.
• Balance only; no quality knob — a size outside the model’s table returns 400.

All models — in the catalog. The general image workflow — images guide.