This section provides detailed information about the image formats and compressions that ImageGear supports.

• File Formats provides background information about different types of file formats, and contains additional topics that provide information on the following:
  • What's the Best Format for...? lists which formats best support various types of images (for example, which formats support an alpha channel). This section provides you with a starting point for deciding which file formats to use in your application.
  • Format Bit Depths is a table that lists the bit depths and the read/write capabilities of the supported formats. Using this table, you can easily find out whether an image can be converted to a particular format.
  • File Formats Reference provides information about every ImageGear supported format, its ID, supported versions, encoding type, multi-page and alpha channel support, supported compressions, color spaces and bit depths for read and write, as well as information about ImageGear supported features and filter control parameters.
  • Metadata Structures provides detailed information about ImageGear supported metadata.
• Compressions provides information about every ImageGear supported imaging compression.

This topic provides information about the following:

• Supported Formats and Compressions
• Encoding vs. Compressing

Supported Formats and Compressions

ImageGear supports the following formats and compressions in the following categories:

• Raster Color and Grayscale
• Vector
• Compressions

  Raster Color and Grayscale

  Format	Full Name	Support
  BMP	Microsoft Windows Bitmap	RW
  CLP	Windows Clipboard	RW
  CUR	Windows cursor	RW
  DIB	DIB (Microsoft Windows Device Independent Bitmap)	RW
  DNG	Digital Negative file format	R
  GIF	CompuServe Graphics Interchange Format (GIF)	RW
  JPEG	JPEG File Interchange Format	RW
  TIFF	Tagged Image File Format	RW

  Vector

  Format	Full Name	Support
  PDF	Adobe Portable Document Format	RW

  Compressions

  Format	Full Name	Formats Supported
  CCITT Group 3 Compression	CCITT Group 3	Adobe PDF, PS, TIFF
  CCITT Group 3 2D Compression	CCITT Group 3 2D	Adobe PDF, PS, TIFF
  CCITT Group 4 Compression	CCITT Group 4	Adobe PDF, PS, TIFF
  Deflate Compression	Deflate Compression	PDF, PS, TIFF, PNG
  Huffman Compression	Huffman Encoding	TIFF
  JPEG Compressions "Lossy" JPEG Compression Lossless JPEG Compression Progressive JPEG Compression	JPEG Compression	Lossy: JPEG, DNG, Adobe PDF, TIFF Lossless: JPEG, TIFF Progressive: JPEG
  LZW (Lempel-Ziv-Welch) Compression	Lempel-Zif-Welch (LZW) Compression	GIF, Adobe PDF, PS, TIFF
  Packbits Compression	Packed Bits Compression	TIFF
  RLE Compression	Run Length Encoding Compression	BMP, CLP, Adobe PDF

  Encoding vs. Compressing

  These two words are often used interchangeably in discussions of graphics file formats. Encoding is actually a broad term under which compression falls. For the sake of clarity, use these terms separately with the following intended meanings:

  • Encoding - The manner that data is stored when uncompressed (binary, ASCII, etc.), how it is packed (e.g., 4-bit pixels may be packed at a rate of two pixels per byte), and the unique set of symbols used to represent the range of data items.
  • Compressing - A "physical" rewriting of the graphics data so that it is represented by a smaller set of data.