API Reference

Output format.

One of: jpg · png · webp · avif · jxl

Target height in pixels. Omit or set to 0 for unconstrained.

Saliency-guided background softening. The subject is left untouched and encoded at quality; the background is lightly low-passed so it costs fewer bytes (roughly 15–40% smaller, depending on format and how much of the frame is background). The background does come out slightly softer. Skipped when there is no clear subject, the subject fills the frame, the background was removed, HDR is being carried, or lossless is set: see X-Mochify-SmartCompress. Accepts 1 or true.

Crop to a rectangle you choose, as four comma-separated fractions of the image: x,y,w,h from the top-left corner (0.25,0.5,0.5,0.5 is the middle of the bottom half). Built for a caller whose own vision model picks the box, as in "crop to the feet": Mochify receives four numbers, never the image description.

Measured on the image as it displays upright, after EXIF orientation, and applied before everything else: width and height then size the region, smartCrop searches inside it, and rotate turns the result. A box running past an edge is trimmed to the image. Any value above 1 is a 400, because that is a pixel coordinate and would otherwise crop the wrong corner without complaint. Check X-Mochify-Region for the pixel rectangle actually cut.

How hidden areas look: fill (solid black) or blur. Requires redact.

Use fill for anything that must stay secret. blur is a cosmetic look: blurred text and faces can sometimes be partly recovered.

Change an object's color and keep its shading: a ;-separated list of up to 8 x,y,w,h:#rrggbb entries (box in the region convention, target color as hex), e.g. 0.4,0.5,0.3,0.2:#2563eb. Paid plans.

Mochify finds the object's outline inside each box and changes only the object, never the rectangle: its hue becomes the target's, and its lightness and saturation shift to the target's while every fold, highlight and texture keeps its place. Not generative. Box exactly the part to recolor (the jacket, not the whole person): everything inside the outline takes the color. A box with no clear object is skipped, not recolored. Applied after erase, before redact and region. Metadata is always stripped and HDR dropped. Check X-Mochify-Recolored and X-Mochify-Recolor-Skipped.

Fill behind transparent areas when the output cannot keep them: every jpg output with transparency, such as an SVG. With removeBackground it also replaces the transparent background on png, webp, avif and jxl output. Otherwise those formats keep the alpha channel and ignore it.

One of: black · a six-digit hex color, with # written as %23 (%23F5F5F5) · transparent. Any other value, including color names and three-digit hex, fills white.

Strip EXIF metadata from the output. Set to false or 0 to preserve metadata.

Exposure adjustment. Range -100 (darkest) to +100 (brightest). 0 is no change.

Ultra HDR / ISO 21496-1 gain map handling. 1 or true preserves a gain map the source already has and never invents one, so it is ignored if the source is not HDR. generate does that and synthesizes a gain map when the source is plain SDR.

Only jpg output can carry a gain map (jxl carries HDR by a different route; avif, webp and png cannot). Skipped when combined with brightness, clarity or removeBackground, since those change the base the gain map is a ratio to. Check X-Mochify-HDR for what was actually emitted.

Lossy PNG. Accepts 1 or true. Reduces the image to a dithered palette of up to 256 colors and emits an indexed PNG, typically 4–5× smaller than the lossless encode.

Without it a png is always pixel-exact, and quality alone never makes it lossy. With it, quality picks the palette size: omitted means the full 256 colors; 80 ≈ 108, 65 ≈ 56, 20 = 8. Applies to png outputs only: a request with no png output is a 400, and in a multi-variant request only the png entries are quantized. Cannot be combined with lossless (a 400). Alpha is preserved. Check X-Mochify-Quantize for what was actually emitted.

Which knob targetBytes may turn: quality (re-encode lower, never resize), dimensions (downscale, never change quality), or both (quality first, then downscale).

Requires targetBytes. For png the quality lever is palette quantization: the pixel-exact encode is tried first, and the file is quantized only if that misses the ceiling (see quantize); dimensions keeps a png pixel-exact. The dimensions lever is also withheld when an HDR gain map is being carried (hdr=1 on an Ultra HDR source), because resizing the base would invalidate the map: quality alone is used, and the target may report floor. When the lever moves, X-Mochify-Target-Scale reports how far.

jpegli quality for the re-encode (1–100). Lower is smaller.

Absolute backstop applied alongside maxDpi: no image keeps a side longer than this. It is what limits an image the placement scan never saw drawn. Set 0 to remove the cap.

Resizing is layout-safe: a PDF image is drawn into the unit square, so changing its pixel size cannot move or rescale it on the page.

Output format for the extracted files.

One of: original · png · jpg · webp · avif · jxl

original copies each embedded JPEG out byte-for-byte, with no re-encode and no quality loss; images stored in other encodings come out as lossless PNG. Setting maxWidth forces a re-encode.

Cap the width of each extracted image, preserving aspect ratio. 0 leaves sizes alone.

Output image format for each rendered page.

One of: png · jpg · webp · avif · jxl

Output quality (1–100). Ignored for png.

Page size. fit makes each page exactly the image, with no whitespace.

One of: fit · a4 · letter

Pixels per inch used to size a fit page, 36–600.

Set to 0 to get one single-page PDF per image, returned as a ZIP, instead of one combined document.

Write the result to your connected storage instead of returning it. One of bucket or drive. The response becomes a JSON receipt, { "stored": true, ... }, and the bytes go straight from Mochify to your storage rather than back through the browser.

Only the operations that produce a single file accept it: op=optimize, and op=create with combine=1. extract, rasterize, split and combine=0 return an archive and are refused with a 400 rather than filed under a made-up name.