In this activity we will be dealing with different Image Types and Formats. Image Types come in four different types:
a. Binary Images
b. Grayscale Images:
c. Truecolor Images
d. Indexed Images
Details:
Item Type: JPEG Image
Size: 1.10 MB
Dimensions: 1920 pixels x 1200 pixels
Horizontal Resolution: 96 dpi
Vertical resolution: 96 dpi
Bit Depth: 24
Anyway here is a camera image of my family's dog, Tami. The details are as follows.
Details:
Item Type: JPEG Image
Size: 3.00 MB
Dimensions: 4608 pixels x 3456 pixels
Horizontal Resolution: 180 dpi
Vertical resolution: 180 dpi
Bit Depth: 24
Resolution unit: 2
Color representation: sRGB
Compressed bits/pixel: 3
Camera maker: Canon
Camera model: Canon PowerShot A4000 IS
F-stop: f/3
Exposure time: 1/8 sec.
ISO speed: ISO-400
Exposure bias: 0 step
Focal length: 5 mm
Max. aperture: 3.15625
Metering mode: Pattern
Flash mode: No flash, compulsary
In this activity, we will be experimenting with different file formats. There are many file formats. File Formats are categorized as either Raster or Vector. Raster types describes the characteristics of each individual pixels. Vector formats, on the other hand contain a geometric description that can be rendered smoothly at any display size. [2] Some popular Raster formats include: JPEG, TIFF, RAW, GIF, BMP, PNG, PAM, WEBP. Vector Format images need to be "rasterized" be displayed on digital monitors. Cathode Ray tube technology (such as in radars, video games, medical monitors) make heavy use of Vector formats. Examples of Vector formats include CGM (computer graphics metafile), SVG, and Gerber File formats.
The scope of this activity will unfortunately fall only on Raster file formats, specifically, PNG, JPEG, TIFF, and BMP.
Here is an image of Juggernaut Dota 2 hero originally in PNG file file, courtesy of http://kkcdn-static.kaskus.co.id/images/2012/07/30/1101061_20120730125032.png
Here is the same file converted to
a. JPEG
Dimensions: 481 x 432
Size: 39.3 KB
Bit Depth: 24
b. GIF
Dimensions: 481 x 432
Size: 42.7 KB
Bit Depth: 8
c. Bitmap Image - 24-bit
Dimensions: 481 x 432
Size: 205 KB
Bit Depth: 8
d. Bitmap Image - 16 Color-bit
Dimensions: 481 x 432
Size: 103 KB
Bit Depth: 4
e. Bitmap Image - Monochrome bitmap
Dimensions: 481 x 432
Size: 27 KB
Bit Depth: 1
PNG or Portable Network Graphics supports lossless data compression. It was created to improve and replace GIF (Graphics Interchange Format). PNG is used for the 2D interlacing method, the cross-platform gamma correction, and the ability to make anti-aliased balls, buttons, text and other graphic elements. It is currently the most lossless data compression image file format on the web. PNG started in 1977 and 1978 when two Israeli researchers, Jacob Ziv and Abraham Lempel, first published a pair of papers on a new class of lossless data-compression algorithms, now collectively referred to as ``LZ77'' and ``LZ78.'[3]
In 1983, Terry Welch of Sperry (which later merged with Burroughs to form Unisys) developed a very fast variant of LZ78 called LZW.[3]
JPEG or Joint Photographic Experts Group images allow tradeoff between quality image and file size. JPEG allows 10:1 compression ratio. JPEG utilizes Discrete Cosine Transform which mathematically converts each frame from spatial (2D) domain to frequency domain.
GIF (Graphics Interchange Format) is a bitmap image format created in 1987. It was originally called 87a. Later, 89a added support for animation delays, transparent background color, and storage of application-specific metadata. [4] As of now all relevant patents have expired. GIF's are now widely used for its simple animation found in websites such as 9gag.
Sources:
1.http://web.archive.org/web/20080610170124/http://www.codersource.net/csharp_color_image_to_binary.aspx
2. A4 - Image Types and Formats 2013.pdf, Soriano, Jing
3. History of the Portable Network Graphics, Greg Roelofs, http://linuxgazette.net/issue13/png.html
4. Graphics Interchange Format, Version 89a, 1 July 1990 Retrieved 6 March 2009
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