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Image file formats

Page history last edited by Jayashree Balaji 13 years, 2 months ago

Raster Image formats

 

Raster files (also called bitmapped files) contain graphics information described as pixels, such as photographic images.  Raster graphics are digital images created or captured (say by scanning a photo) as a set of samples of a given space. A raster is a grid of x and y coordinates on a display space. A raster file is usually larger than a vector graphics image file. A raster file is usually difficult to modify without loss of information, although there are software tools that can convert a raster file into a vector file for refinement and changes. Given below are examples of raster file formats:

 

JPEG/JFIF

JPEG (Joint Photographic Experts Group) is a compression method; JPEG-compressed images are usually stored in the JFIF (JPEG File Interchange Format) file format. JPEG compression is (in most cases) lossy compression. Nearly every digital camera can save images in the JPEG/JFIF format, which supports 8 bits per color (red, green, blue) for a 24-bit total, producing relatively small files. When not too great, the compression does not noticeably detract from the image's quality, but JPEG files suffer generational degradation when repeatedly edited and saved.

 

   Image source : http://en.wikipedia.org/wiki/JPEG

 

Exif

The Exif(Exchangeable image file format) format is a file standard similar to the JFIF format with TIFF extensions; it is incorporated in the JPEG-writing software used in most cameras. Its purpose is to record and to standardize the exchange of images with image metadata between digital cameras and editing and viewing software. The metadata are recorded for individual images and include camera settings, time and date, shutter speed, exposure, image size, compression, name of camera, color information, etc. When images are viewed or edited by image editing software, all of this image information can be displayed.

 

TIFF

The TIFF (Tagged Image File Format) format is a flexible format that normally saves 8 bits or 16 bits per color (red, green, blue) for 24-bit and 48-bit totals, respectively, usually using either the TIFF or TIF filename extension. TIFFs are lossy and lossless; some offer relatively good lossless compression for bi-level (black&white) images. The TIFF image format is not widely supported by web browsers. TIFF remains widely accepted as a photograph file standard in the printing business.

 

PNG

The (Portable Network Graphics) file format is the free, open-source successor to GIF for the lossless, portable, well-compressed storage of raster images. The PNG file format supports truecolor (16 million colors) while the GIF supports only 256 colors. The PNG file excels when the image has large, uniformly colored areas. The lossless PNG format is best suited for editing pictures, and the lossy formats, like JPG, are best for the final distribution of photographic images, because JPG files are smaller than PNG files. All contemporary web browsers now support the PNG format, so it works well in online viewing applications. PNG is robust, providing both full file integrity checking and simple detection of common transmission errors.

 

GIF

The Graphics Interchange Format is limited to an 8-bit palette, or 256 colors. This makes the GIF format suitable for storing graphics with relatively few colors such as simple diagrams, shapes, logos and cartoon style images. The GIF format supports animation and is still widely used to provide image animation effects. It also uses a lossless compression that is more effective when large areas have a single color, and ineffective for detailed images.

 

BMP 

The BMP (Windows bitmap) handles graphics files within the Microsoft Windows OS. Typically, BMP files are uncompressed, hence they are large; the advantage is their simplicity and wide acceptance in Windows programs.

 

Vector Image formats

Unlike raster image formats, vector image formats contain a geometric description which can be rendered smoothly at any desired display size. 3D graphic file formats are technically vector formats, vector file formats can contain bitmap data as well.

 

CGM

CGM (Computer Graphics Metafile) is a file format for 2D vector graphics, raster graphics, and text. CGM provides a means of graphics data interchange for computer representation of 2D graphical information independent from any particular application, system, platform, or device. It has been superseded by formats such as SVG.

 

SVG

SVG (Scalable Vector Graphics) is an open standard created and developed by the World Wide Web Consortium to address the need for a versatile, scriptable vector format for the web. The SVG format does not have a compression scheme of its own, but due to the textual nature of XML, an SVG graphic can be compressed using a program such as gzip. Because of its scripting potential, SVG is a key component in web applications such as interactive web pages that look and act like applications.

 

 

 

Image Source: http://en.wikipedia.org/wiki/Scalable_Vector_Graphics

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