Image formats

• Adobe Photoshop (*.psd)

  Adobe Photoshop (PSD) is the format produced by the Adobe Photoshop graphics editor.

• Tagged Image File Format (*.tif, *.tiff)

  TIFF (Tag Image File Format), pronounced "tiff," was originally developed by Aldus Corporation to save images created by scanners, frame grabbers, and photo editing programs. This format has been widely accepted and widely supported as an image transfer format not tied to specific scanners, printers, or computer display hardware. TIFF is also a popular format for desktop publishing applications. There are several variations of the format, called extensions, so you may have occasional problems opening one from another source. Some versions are compressed using the LZW or other lossless methods. TIFF files support up to 24-bit colors.

• PCX Image format (*.pcx)

  This is a file format created by ZSoft. This format compresses its image data with the RLE type compression.

• JPEG image (*.jpg, *.jpeg)

  The JPEG (Joint Photographic Experts Group) format, pronounced "jay-peg," is by far the most popular format for display of photographic images on the Web. The term "JPEG" is often used to describe the JFIF file format (JPEG File Interchange Format). JFIF is the actual file format that contains an image compressed with the JPEG method. These newer JFIF files originally used the JPG extension, however, the latest standard calls for using a JIF extension instead. The format is optimized for the display of photographs and doesn't work as well as GIF for type or line drawings (GIF is optimized for those). JPEG images have two distinctive features:

  JPEG uses a lossy compression scheme but you can vary the amount of compression and hence trade off file size for image quality, even making extremely small files with poor quality.
  JPEG supports 24-bit color. GIF, the other format widely used on the Web supports only 8-bits.
  Compression is performed on blocks of pixels eight on a side. You can see these blocks when you use the highest levels of compression or greatly enlarge the image. JPEG is a two pass compression and de-compression algorithm. This means it take longer to load and display than a gif file. You can save images in a progressive JPEG format that works somewhat like an interlaced GIF. While a standard JPEG loads from top to bottom, a progressive JPEG displays the entire image starting with the largest blocks. This allows the image to be displayed first in low-resolution and then filled in as more data arrives. When you save an image in this format, you can specify the number of progressive scans. Don't use JPEG to save original images you expect to modify later. Every time you open one of these files, and then save it again, the image is compressed. As you go through a series of saves, the image become more and more degraded. Be sure to save your originals is a loss-free format such as TIFF or BMP at maximum color depth. Also, when you save an image as a JPEG, the image on the screen won't reflect the compression unless you load the saved version.

• Portable Network Graphics (*.png)

  PNG (Portable Network Graphics), pronounced "ping," has been developed to replace the aging GIF format and it is supported by both Microsoft Internet Explorer and Netscape Navigator. PNG, like GIF is a lossless format, but it has some features that the GIF format doesn't. These include 254 levels of transparency (GIF supports only one), more control over image brightness, and support for more than 48 bits per pixel. (GIF supports 8 for 256 colors). PNG also supports progressive rendering, as interlaced GIFs do, and tends to compress better than a GIF.

• Windows Bitmap (*.bmp)

  BMP, pronounced a letter at a time "B-M-P," files use a Windows bitmap format. These images are stored in a device-independent bitmap (DIB) format that allows Windows to display the bitmap on any type of display device. The term "device independent" means that the bitmap specifies pixel color in a form independent of the method used by a display to represent color. The default filename extension is .BMP and these files come in two formats:

  The OS/2 format is not compressed (RGB encoded). RGB encoding supports 24-bit colors.
  Windows BMP and DIB files may be saved using no compression (RGB encoded), or using run length encoded lossless compression (RLE encoded). RLE supports only 256 colors.
  Windows can store color data along with the image it affects. When stored like this, the images is called a Microsoft Device Independent Bitmap, or DIB. When written out to a file, it in the Microsoft Bitmap Format, or BMP. References to the DIB file format actually refer to BMP.

  Windows RLE files are Windows DIB files that use RLE compression. Using RLE compressions to save an image as a DIB or BMP, produces an RLE file. The only difference is the filename extension.

• True Vision Targa (*.tga)

  TGA or TARGA format is a format for describing bitmap images, it is capable of representing bitmaps ranging from black and white, indexed colour, and RGB colour, the format also supports various compression methods. This note describes the minimal requirements for creating a TGA file for a 24 bit RGB uncompressed colour image, this covers most applications where a developer might want to create an image for another package which reads TGA files

• Compuserve GIF(*.gif)

  GIF (Graphics Interchange Format) format images, pronounced "jiff," are widely used on the Web but mostly for line art, not for photographic images. This format stores up to 256 colors from an image in a table called a palette. Since images have millions of colors, a program such as PhotoShop selects the best ones to represent the whole when you save the image in this format. When displayed, each pixel in the image is then displayed as one of the colors from the table, much like painting by numbers.

  There are two versions of GIF in use on the Web; the original GIF 87a and a newer GIF 89a. Both versions can use interlacing; storing images using four passes instead of one. Normally, when an image is displayed in a browser, it is transmitted a row at a time starting at the top row and filling in down the page. When saved as an interlaced GIF, it is first sent at its full size but with a very low resolution. This allows a person to get some idea of all of the contents of the image file before it is completely transmitted. As more pixels are sent in the next three passes the image fills in and eventually reaches its full resolution. The newer GIF 89a version adds some additional capabilities that include the following:

Image backgrounds can be made transparent. To do so, you specify which color in the table is to be transparent. When viewed with a Web browser, the browser replaces every pixel in the image that is this color with a pixel from the web page's background. This allows the background to show through the image in those areas. You have to choose the transparent color carefully. If you select one that occurs anywhere in the image besides the background, your image will appear to have "holes" in it.
Images can be animated. By rapidly "flipping" through a series of images, objects can be animated much as a movie simulates motion using a series of still images. This works best with line drawings but can also be done with photographs. Depending on bandwidth, the animation may not work the first time. However, once it's stored in cache and replayed, it will work fine.

GIF images are limited to a maximum of 256 colors. These colors, stored in a table, index, or palette, are often referred to as indexed colors. When you convert a photograph to GIF format, most graphics programs will allow you to dither it. This replaces lost colors with patterns of those available in the palette. Dithering improves the appearance of the image, but it also increases the size of the file. Although GIF photographs often look OK on-screen, they suffer if compared side-by-side with images saved in JPEG and other formats. The GIF format is best used for line art such as cartoons, graphs, schematics, logos, and text that have a limited number of colors and distinct boundaries between color regions. GIF images are compressed using a "lossless" form of compression called LZW (Lempel-Ziv-Welch). The amount of compression achieved depends on the frequency of color changes in each pixel row. This is because when two or more pixels in a row have the same color, they are recorded as a single block. Hence, a picture of horizontal stripes will compress more than one of vertical stripes, because the horizontal lines would be each stored as a single block. Photographs with large areas of identical colors such as skies, snow, clouds, and so on, will compress more than images with lots of colors and patterns. To save a 24 bit image as a GIF, you must reduce the bit depth down to 8 bits. To reduce file sizes in GIF format, you can further reduce the number of colors in the image. This is difficult with most photographs, but not with line art. For example, if your image has 16 or fewer colors, you can convert it to a 4-bit (16-color) palette. Most graphics programs will allow you to do this. Even with photographs you can sometimes reduce the image to fewer colors than actually exist without noticeable loss. The discarded colors are those that are seldom-used or transitional colors between more frequent colors. When working with grayscale images, GIF works as well as JPEG because almost all programs use 8-bits (256 colors) for gray scale images.

Video formats: (Note: Unique feature!!!)

• Video for Windows(*.avi)

  AVI format Description

  One of the oldest formats in the x86 computer world is AVI. The abbreviation 'AVI' stands for 'Audio Video Interlaced'. This video format was created by Microsoft, which was introduced along with Windows 3.1. AVI, the proprietary format of Microsoft's "Video for Windows" application, merely provides a framework for various compression algorithms such as Cinepak, Intel Indeo, Microsoft Video 1, Clear Video or IVI. In its first version, AVI supported a maximum resolution of 160 x 120 pixels with a refresh rate of 15 frames per second. The format attained widespread popularity, as the first video editing systems and software appeared that used AVI by default. Examples of such editing boards included Fast's AV Master and Miro/Pinnacle's DC10 to DC50. However, there were a number of restrictions: for example, an AVI video that had been processed using an AV Master could not be directly processed using an interface board from Miro/Pinnacle. The manufacturers adapted the open AVI format according to their own requirements.

  AVI is subject to additional restrictions under Windows 95, which make professional work at higher resolutions more difficult. For example, the maximum file size under the FAT16 file system is 2 GB. The FAT32 file system (came with OSR2 and Windows 98) brought an improvement: in connection with the latest DirectX6 module 'DirectShow', files with a size of 8 GB can (at least in theory) be created. In practice however, many interface cards lack the corresponding driver support so that Windows NT 4.0 and NTFS are strongly recommended. Despite its age and numerous problems, the AVI format is still used in semi-professional video editing cards. Many TV cards and graphic boards with a video input also use the AVI format. These are able to grab video clips at low resolutions (mostly 320 x 240 pixels).

  AVI is a file format, like MP3 or JPG. But unlike these formats, AVI is a container format, meaning it can contain video audio compressed using many different combinations of codecs. So while MP3 and JPG can only contain a certain kind of compression (MPEG Audio Layer 3 and JPEG), AVI can contain many different kinds of compression (eg. DivX video + WMA audio or Indeo video + PCM audio), as long as a codec is available for encoding/decoding. AVI all look the same on the "outside", but on the "inside", they may be completely different. Almost all tools on this site are not just DivX tools, but also AVI tools, so will probably work with other codecs. There is no such thing as a "normal" AVI file, but the closest you can get is probably an AVI file that contains no compression. AVI files has been around since the time of Windows 3.1, so by no means is it a new thing, and is probably the most common video format around (although its popularity wavered a few years ago, but has since come back with a vengeance due to the emergence of DivX). AVI files may also have limits under Windows 95/98, and for more information, please read this article. Note that AVI files without file limits (other than the Windows Fat32 file limit) are usually referred to as OpenDML AVI files.

• MPEGG Video File Format (*.mpg, *.mpeg)

  MPEG-4 is an ISO/IEC standard developed by MPEG (Moving Picture Experts Group), the committee that also developed the Emmy Award winning standards known as MPEG-1 and MPEG-2. These standards made interactive video on CD-ROM, DVD and Digital Television possible. MPEG-4 is the result of another international effort involving hundreds of researchers and engineers from all over the world. MPEG-4, with formal as its ISO/IEC designation 'ISO/IEC 14496', was finalized in October 1998 and became an International Standard in the first months of 1999. The fully backward compatible extensions under the title of MPEG-4 Version 2 were frozen at the end of 1999, to acquire the formal International Standard Status early in 2000. Several extensions were added since and work on some specific work-items work is still in progress.
  MPEG-4 builds on the proven success of three fields:
  Digital television;
  Interactive graphics applications (synthetic content);
  Interactive multimedia (World Wide Web, distribution of and access to content)
  MPEG-4 provides the standardized technological elements enabling the integration of the production, distribution and content access paradigms of the three fields.