Licensing options for this format begin with FME Desktop Professional Edition.
The JPEG Reader/Writer provides FME with access to data in the JPEG format.
Overview
JPEG (Joint Photographic Experts Group) is a standardized image compression mechanism. JPEG is designed for compressing either full-color three-band (RGB) or gray-scale one-band images. JPEG data can be either 8 or 12-bit. JPEG compression can make a file very small, but it is “lossy,” meaning that image quality is lost when the image is compressed. The current version of this format supports reading, writing, but not update in place. There is currently no support for georeferencing information or metadata for JPEG files.
The current version of this format supports reading, writing, but not update in place. There is currently no support for georeferencing information or metadata for JPEG files.
Format Parameters
The JPEG writer supports the following additional options through the Feature Type dialog:
World File
This option enables the generation of an associated Esri world file (.wld)
Compression Level
This option sets the desired compression level of the output image. This is expressed as a percentage of the original file size. For example, setting a compression level of 75 means that the output image will be approximately 75% smaller (one-quarter of the size) than an uncompressed image.
Note that this value only represents the targeted compression level, and this may not actually be achieved. JPEG supports both lossy and lossless compression. With lossy compression, the compressed image is an approximation of the original. With lossless compression, the compressed image is identical to the original.
Note: Repeatedly reading and saving files may decrease the quality for this format. In addition, Workbench may not know which format data comes from, and whether it used lossy compression. If you know that source data comes from files with lossy compression, you should also set the compression level to 0. Although this compression still does not guarantee the exact copy of the source file, the output will be very close to the original.
Reader Overview
The FME considers a single JPEG file to be a dataset. The JPEG file contains pixel data. Each pixel in the file is a point in a single FME raster feature.
Writer Overview
FME considers a writer dataset to be a folder name. The JPEG writer distinguishes duplicate output files by appending numbers to the filenames.
FME Raster Features
JPEG files can only be created with square pixel dimensions.
JPEG supports rasters with either a Red8, a Green8, and a Blue8 band, or a single Gray8 band.
FME raster features represent raster data and use several concepts that are unlike those used in the handling of vector data. The topics below describe how FME processes raster data.