Photography > File Formats

When dealing with graphic files the file can be very confusing. There are several diferent types of file formats. In this section we will define the most common file formats and briefly explain which one we need to develop your web site. So let us start by defining some commonly used terms seen today.

Bitmap -
images contain many individual pixels with each pixel containing a color which is stored in one or more bits of data. For example, a 1-bit image assigns each pixel a black or white value and a 4-bit image assigns each pixel one of 16 color values and so on.

Vector Graphic Files -
(one of two methods used to represent images) are represented as mathematical formulas that define all the shapes of the image. Vector graphic files will look the same even when scaled up or down to different sizes.

Raster Graphic Files -
describe shapes as a pattern of dots or pixels and tend to become ragged-edged when resized. Bit mapped images are often referred to as raster graphics.

Compression -
the ability to shrink a large sized image can be done in two different ways- Loss Less Compression and Lossy Compression. Each pixel is encoded in an uncompressed image. Loss Less Compression takes this a step further and finds pixels of the same value and encodes them as well, insuring that the file, when decompressed, will look identical to it's original file.

Lossy Compression -
used in JPEG formats, loses information when compressing the file and when uncompressed, shows little or no degradation of the image. How? Graphic images represent more colors than the human eye can see; therefore, what is lost at retrieval was never really seen to begin with.

 

Now onto some of the many different image file formats used today.

BMP (Windows Bitmap) -
This is the standard file format used by Microsoft Windows. This file can contain 2 colors (black and white) or up to 16.7 million colors. Most BMP files are not compressed. A variation to BMP files is the RLE file. This file offers a small degree of image compression and can be used to create compressed wallpaper files. RLE files are either 16 or 256 color image files. The file extensions for both are .bmp and .rle

GIF (CompuServe Graphics Interchange Format) -
GIF files can have anywhere from 2 to 256 colors. It was created by CompuServe for their online service and is now the standard file format for most online services. GIF files have a high compression rate and are an efficient way to store larger image sizes. The file extension is .gif

JPEG (Joint Photographic Experts Group) -
JPEG files use a method of compression that reduces image file size by selectively reducing the amount of detail contained in the image, Lossy Compression. As mentioned before, what is left out is beyond the range of human vision. JPEG files are either true color or grayscale. The file extension is .jpg

Encapsulated PostScript (EPS) -
The Encapsulated PostScript format is a vector file relying on the PostScript page description language to draw its image. This format can also contain raster information, even though it's not a raster format. EPS files generally contain a raster graphic as a screen preview-Mac EPS files use a PICT and PC EPS files use a TIFF graphic. EPS is the only format that supports transparent white in bitmap model.

PCX (PC Paintbrush) -
These files come in monochrome, 16 or 256 color and true color (24-bit). The PCX file was originally created for the PC Paint Brush package. The files are modestly compressed and the file extension is .pcx

TIFF (Tagged Image File Format) -
TIFF files are versatile and supports almost any picture bit depth. The files come in monochrome, 16 and 256 colors, 16 and 256-grayscale color and true color (24-bit). TIFF files can be saved in compressed or uncompressed formats with the compressed format having a high degree of compression. The file extension is .tif