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Appengine URL parameters for images

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xnopasaranx edited this page Oct 31, 2018 · 2 revisions

There are a couple of useful but undocumented options with which one can request an image to be served. These options have been taken from this stackoverflow post so please be aware of the following caveats and do not use them lightheartedly:

Caveats

Some options (like =l for JPEG quality) do not seem to generate new images. If you change another option (size, etc.) and change the l value, the quality change should be visible. Some options also don't work well together. This is all undocumented by Google, probably with good reason. It's probably not a good idea to depend on any of these options existing forever. Google could remove most of them without notice at any time.

SIZE / CROP

  • s640 — generates image 640 pixels on largest dimension
  • s0 — original size image
  • w100 — generates image 100 pixels wide
  • h100 — generates image 100 pixels tall
  • s (without a value) — stretches image to fit dimensions
  • c — crops image to provided dimensions
  • n — same as c, but crops from the center
  • p — smart square crop, attempts cropping to faces
  • pp — alternate smart square crop, does not cut off faces (?)
  • cc — generates a circularly cropped image
  • ci — square crop to smallest of: width, height, or specified =s parameter
  • nu — no-upscaling. Disables resizing an image to larger than its original resolution.

PAN AND ZOOM

  • x, y, z — pan and zoom a tiled image. These have no effect on an untiled image or without an authorization parameter of some form (see googleartproject.com).

ROTATION

  • fv — flip vertically
  • fh — flip horizontally
  • r{90, 180, 270} — rotates image 90, 180, or 270 degrees clockwise

IMAGE FORMAT

  • rj — forces the resulting image to be JPG
  • rp — forces the resulting image to be PNG
  • rw — forces the resulting image to be WebP
  • rg — forces the resulting image to be GIF
  • v{0,1,2,3} — sets image to a different format option (works with JPG and WebP) Forcing PNG, WebP and GIF outputs can work in combination with circular crops for a transparent background. Forcing JPG can be combined with border color to fill in backgrounds in transparent images.

ANIMATED GIFs

  • rh — generates an MP4 from the input image
  • k — kill animation (generates static image)

MISC.

  • b10 — add a 10px border to image
  • c0xAARRGGBB — set border color, eg. =c0xffff0000 for red
  • d — adds header to cause browser download
  • e7 — set cache-control max-age header on response to 7 days
  • l100 — sets JPEG quality to 100% (1-100)
  • h — responds with an HTML page containing the image
  • g — responds with XML used by Google's pan/zoom

Filters

  • fSoften=1,100,0 - where 100 can go from 0 to 100 to blur the image
  • fVignette=1,100,1.4,0,000000 - where 100 controls the size of the gradient and 000000 is RRGGBB of the color of the border shadow
  • fInvert=0,1 inverts the image regardless of the value provided
  • fbw=0,1 makes the image black and white regardless of the value provided

Unknown Parameters

These parameters have been seen in use, but their effect is unknown: no, nd, mv

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