Foundations of Digital Image

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03. Formats

In this chapter, various image file formats are listed and explained. Image files, like any other digital files, are composed of digital data. These formats can be rasterized for use on a computer display or printer. The formats are standard means of organizing and storing digital images and each format employs a different algorithm, which means they follow different methodologies to provide different strengths. An image file format may store data in uncompressed, compressed, or vector formats.

There is a table at the end of this chapter to show raster, vector, or hybrid formatting capabilities of different files types.

Bitmap is a type of memory organization or image file format used to store digital images. The term bitmap comes from computer programming terminology, meaning a map of bits or a spatially mapped array of bits. Many of the file formats listed and explained in this chapter, such as GIF, PNG, TIFF, and JPEG, are also bitmap file formats that work using different compressions and algorithms to serve different purposes.

 

BMP

BMP is an image file format used to store bitmap digital images. Simply, a bitmap is a raster graphics image file format used to store bitmap digital images independently of the display device. The main property of this format is that it encloses 1 bit per pixel, so it is a pretty reliable and predictable format for developers.

 

TIFF

TIFF, Tagged Image File Format, is a file format for handling images and data within a single file. It includes the header tags (size, definition, image-data arrangement, applied image compression) to define the image’s geometry.

The ability to store image data in a lossless format makes a TIFF file useful for image archiving and print publishing. Unlike standard JPEG files, a TIFF file using lossless compression (or none) may be edited and re-saved without losing any information of the image.

This is not the case when using the TIFF as a container holding a compressed JPEG. Other TIFF options are layers and pages. TIFF offers the option of using LZW compression, a lossless data compression technique for reducing file size. Most of the modern web browsers don’t recognize TIFF and display images in this format.

 

JPG

The term “JPEG” is an acronym for the Joint Photographic Experts Group, which created the standard. The format is often used with the “.jpg” extension.

JPEG is optimized for photographs and similar continuous tone images that contain many, many colors. It can achieve astounding compression ratios even while maintaining very high image quality. JPG works by analyzing images and discarding kinds of information that the eye is least likely to notice. It stores information as 24-bit color. Important: the degree of compression of a JPEG is adjustable. At moderate compression levels of photographic images, it is very difficult for the eye to discern any difference from the original, even at extreme magnification. Compression factors of more than 20 are often quite acceptable.

 

hb_2006.92

 jpeg ny02, 2004 by Thomas Ruff

GIF

GIF are suitable for sharp-edged line art with a limited number of colors, such as logos. It is a raster format designed for displaying vector-like images. This takes advantage of the format’s lossless compression, which favors flat areas of uniform color with well-defined edges. It makes sense to rasterize a simple drawing to compress and display digitally. Up until the emergence of PNG, GIF was the prevalent format for web graphics. Now it is more popular in its animated format.

 

Animated GIF

Basic animation was added to the GIF89a spec via the Graphics Control Extension (GCE), which allows various images (frames) in the file to be painted with time delays. An animated GIF file comprises a number of frames that are displayed in succession, each introduced by its own GCE, which gives the time delay to wait after the frame is drawn. Global information at the start of the file applies by default to all frames.

These are tiny animations made from looping together a few still images — like a digital flip book. They have become such an integral part of popular culture that the Oxford English Dictionary named GIF the word of the year for 2012.

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Metro-Goldwyn-Mayer by Jack Goldstein 1975

Short History of GIFs -  http://movingthestill.tumblr.com

DyingGaulwithSprite1_zpsd5555384

Steven Mayer, The Dying Gaul with Sprite, 2012, gif

RecliningCyclopsWeb_zpsd7a1ddf3

Steven Mayer, Reclining Cyclops, 2013, gif

PNG

Portable Network Graphics is a Raster graphics file format that supports lossless data compression. PNG was created as an improved, non-patented replacement for Graphics Interchange Format (GIF), and is the most used lossless image compression format on the World Wide Web.

PNG supports palette-based images (with palettes of 24-bit RGB or 32-bit RGBA colors), grayscale images (with or without alpha channel), and full-color non-palette-based RGB[A] images (with or without alpha channel). PNG was designed for transferring images on the Internet, not for professional-quality print graphics, and therefore does not support non-RGB color spaces such as CMYK.

Untitled-1

PNG offers a variety of transparency options. With true color and grayscale images either a single pixel value can be declared as transparent.

Today, It is the prevailing format for online graphic images.

PDF

Portable Document Format (PDF) is a file format used to represent documents in a manner independent of application software, hardware, and operating systems. Each PDF file encapsulates a complete description of a fixed-layout flat document, including the text, fonts, graphics, and other information needed to display it. It is a self enclosed format which is still transformable to all other formats but it is known as an non-editable format but still there are a few applications such as Acrobat designed for editing these files.

AI

Adobe Illustrator is a proprietary file format developed by Adobe Systems for representing single-page vector-based drawings in either the EPS or PDF formats.

SVG

Scaleable Vector Graphics is an XML-based vector image format for two-dimensional graphics that has support for interactivity and animation.

CRW, DNG AND and RAW are all raw image formats contains minimally processed data from the image sensor of either a digital camera, image scanner, or motion picture film scanner. RAW files are named so because they are not yet processed and therefore are not ready to be printed or edited with a bitmap graphics editor. Different brands develop various different RAW image formats such as Nikon uses DNG whereas Canon is using CRW its self developed format.

EXIF is not an image format, it is often considered as one but it is actually a standard that specifies the formats for images, sound, and ancillary tags used by digital cameras (including smartphones), scanners and other systems handling image and sound files recorded by digital cameras. It contains all the meta data of the digital image.

 

 

 

Raster

 

Vector

AI

 

x

 

x

BMP

 

x

 

 

EXIF

 

 

 

x

GIF

 

x

 

 

JPEG

 

x

 

 

PDF

 

x

 

x

PNG

 

 

 

x

RAW

 

 

 

x

SVG

 

 

 

x

TIFF

 

x

 

 

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