A3.1 The Different Image Types

As part of the third activity, we studied about the 4 different image types and looked for sample images for each type.

Binary images have only 1 bit per pixel and are therefore black OR white images.

http://www.planetoftunes.com/dtp/dtp_media/bitdepth/cat1bit.gif


http://www.pages.drexel.edu/~brooksdr/DRB_web_page/howto/BW_image/BW_program.htm

They should not be confused with Grayscale images which are black AND white images. Grayscale images have 1byte per pixel. This means that each pixel can have can have any value from 0 (black) to 255 (white). Grayscale images are usually used for medical images like the retina ultrasound below.

http://www.drgdiaz.com/images/eye-rbn.shtml

When three grayscale channels, one each for red, green, and blue intensities, are overlaid, a Truecolor image can be produced. Because there are 3 bytes / pixel, Truecolor images can have 256 X 256 X 256 or over 1.6 million possible colors. Images from digital cameras are truecolor images.

http://r0k.us/graphics/kodak/kodim15.html

Because truecolor images require greater memory sizes, sometimes an image may be Indexed to save space. An indexed image contains the image itself and its colormap. All the colors in the image will then be represented by a number which is an index in the colormap.

http://www.sketchpad.net/basics6.htm
http://www.webdesign.org/img_articles/15717/dx-flower-final-other-colors.gif

Reference: Activity 3 Handout