qlt

JPEG quality. Specifies JPEG encoding attributes to control the compression level. This in turn varies the file size (amount of the reply data), and, indirectly, the visual quality of the resultant image.

qlt=quality[,chroma]

quality

JPEG encoding quality (1…100 int).

chroma

JPEG chromaticity down-sampling (0=normal, 1=disable); optional, default is 0.

Higher quality values increase file size and quality, lower values decrease file sizes and reduce perceived image quality. Values above 90 often generate images indistinguishable from the uncompressed image.

Set the chroma flag to disable the RGB chromaticity down-sampling employed by typical JPEG encoders. This may increase the perceived sharpness of edges in an image when the edge is defined by a change in hue rather than brightness. Setting this flag may cause a slight increase in file size. Experiment with this setting if text seems slightly blurry.

Properties

Request attribute. Applies regardless of current layer setting. Ignored if the output image file format does not support JPEG encoding. Refer to the description of fmt= for information on which output image formats support qlt=.

chroma is ignored if the output pixel type is CMYK or gray.

Default

attribute::JpegQuality

Example

Reduce quality for faster transmission over a low-bandwidth connection:

http://server/myRoodId/myImageId?qlt=60&wid=300

Increase quality for high-bandwidth connections:

http://server/myRootId/myImageId?qlt=95,1&wid=300