<html> <head> <title>JPEG -- JPEG JFIF File Format</title> </head> <body bgcolor="#ffffff"> <h1>JPEG -- JPEG JFIF File Format</h1> The JPEG JFIF format is supported for reading, and batch writing, but not update in place. JPEG files are represented as one band (greyscale) or three band (RGB) datasets with Byte valued bands. There is currently no support for georeferencing information or metadata for JPEG files. Overviews can be built for JPEG files as an external .ovr file. The GDAL JPEG Driver is built using the Independent JPEG Group's jpeg library. Also note that the GeoTIFF driver supports tiled TIFF with JPEG compressed tiles. <h2>Creation Options</h2> JPEG files are created using the "JPEG" driver code. Only Byte band types are supported, and only 1 and 3 band configurations. JPEG file creation is implemented by the batch (CreateCopy) method. <ul> <li> <b>QUALITY=n</b>: By default the quality flag is set to 75, but this option can be used to select other values. Values must be in the range 10-100. Low values result in higher compression ratios, but poorer image quality. A value of 100 will result in lossless compression.<p> <li> <b>PROGRESSIVE=ON</b>: Enabled generation of progressive jpegs. In some cases these will display a reduced resolution image in viewers such as Netscape, and Internet Explorer, before the full file has been downloaded. However, some applications cannot read progressive jpegs at all. GDAL can read progressive jpegs, but takes no advantage of their progressive nature.<p> </ul> See Also:<p> <ul> <li> <a href="http://www.ijg.org/">Independent JPEG Group</a> </ul> </body> </html>
