Perform operations similar to those in image-editing applications.

Background &bg=

Sets the background color of the image. Supports a variety of color formats. In addition to the 140 color names supported by all modern browsers (listed here), it also accepts hexadecimal RGB and RBG alpha formats.

Valid hexadecimal formats:

  • 3 digit RGB: CCC
  • 4 digit ARGB (alpha): 5CCC
  • 6 digit RGB: CCCCCC
  • 8 digit ARGB (alpha): 55CCCCCC

More info: Issue #81 - Background setting.

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Blur &blur=

Adds a blur effect to the image. When used without a value (&blur), performs a fast, mild blur of the output image. When a value is provided, performs a slower, more accurate Gaussian blur.

Use values between 0.3 and 1000, representing the sigma of the Gaussian mask, where sigma = 1 + radius / 2.

More info: Issue #69 - Allow blur transformation (with radius parameter).

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Contrast &con=

Adjusts the image contrast. Use values between -100 and +100, where 0 represents no change.

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Filter &filt=

Applies a filter effect to the image. Accepts greyscale, sepia, duotone or negate.


You can use &start and &stop to define the duotone colors. By default, it will use &start=C83658 and &stop=D8E74F.

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Gamma &gam=

Adjusts the image gamma. Use values between 1.0 and 3.0. The default value is 2.2, a suitable approximation for sRGB images.

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Modulate &mod=

Transforms the image using brightness, saturation and hue rotation. Use &mod=[brightness multiplier], [saturation multiplier],[hue degrees] to define the below adjustments at once.

Brightness &mod=

Adjusts the brightness of the image. A multiplier greater than 1 will increase brightness, while a multiplier less than 1 will decrease the brightness.

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Saturation &sat=

Adjusts the saturation of the image. A multiplier greater than 1 will increase saturation, while a multiplier less than 1 will decrease the saturation.

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Hue rotation &hue=

Applies a hue rotation to the image. A positive hue rotation increases the hue value, while a negative rotation decreases the hue value.

Values are given in degrees, there is no minimum or maximum value; &hue=N evaluates to N modulo 360.

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![Hue rotation](
Hue rotation

Sharpen &sharp=

Sharpen the image. Performs an accurate sharpen of the L channel in the LAB color space. Use in combination with &sharpf= and &sharpj= to control the level of sharpening in "flat" and "jagged" areas.

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Tint &tint=

Tint the image using the provided chroma while preserving the image luminance. See here for the supported color formats.

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