Image formats

Supported output image formats

JPEG compression

The JPEG compression format is suitable for delivering photographic images with minimal quality loss and high compression rate. You can either choose the compression factor yourself or use Optipress - our Machine Learning based algorithm, which will choose the best way to reduce JPEG file size minimising perceptual quality loss.

Available parameters

Set format	force_format=jpg	forces using the JPEG image compression
Quality	q=X X=0..100	the smaller the value of q, the more your image will be compressed. Be careful - the quality of the image will decrease as well.
Optipress	optipress=X X=1..3	chooses the best compression approach maintaining visual quality via the Optipress algorithm

Examples

Preview	Syntax
	q=85, filesize 204 kB: /docs/woman_dress.jpg?force_format=jpeg&q=85 q=75, filesize 129 kB: /docs/woman_dress.jpg?force_format=jpeg&q=75 q=65, filesize 102 kB: /docs/woman_dress.jpg?force_format=jpeg&q=65

PNG format

This format is a good choice for non-photographic images - flowcharts, graphs, screenshots, logos, etc. PNG also supports transparency.

Available parameters

Set format

force_format=png

forces using the PNG image compression

Lossy PNG compression

While the PNG format offers lossy compression only, Filerobot can optimize the image before compression by reducing the number of colors or adding slight dithering (while preserving edges). This method usually leads to smaller file sizes for images visually indistinguishable from the original ones.

You can activate this feature in the Asset Hub (Settings/Process/Images/Image compression):

Examples

Preview	Syntax
	/docs/Filerobot_Logo_3000px.png?w=400&force_format=png

WebP format

WebP is an image format maintained by Google and supported in certain browsers (mainly Chrome, Opera and on Chrome Android) which provides more aggressive compression techniques as JPG without noticeable quality degradation.

By default, automatic WebP transcoding is deactivated. If you choose to activate it, all images will be delivered as WebP. If the client's browser does not support this format, JPEG or PNG (if image has alpha channel) is used instead.

You can use the following parameters to control webp compression quality:

Set format	force_format=webp	forces using the JPEG image compression
Quality	q=X X=0..100	the smaller the value of q, the more your image will be compressed. Be careful - the quality of the image will decrease as well.
Lossless	lossless=1	use lossless webp compression

Examples

Preview	Syntax
	/docs/paris.jpg?w=400&force_format=webp
	/docs/perfcheck.png?w=400&force_format=webp&lossless=1

Deliver images in their original format

By default, Filerobot delivers the images as WebP, when the format is supported by the browser. If you would like to keep the format of the original image (when possible), you can use force_format=original.