Practical Image and Video Processing Using MATLAB® Chapter 2 – Image processing basics By Oge Marques Copyright © 2011 by John Wiley & Sons, Inc. All rights reserved. What will we learn?  How is a digital image represented and stored in memory?  What are the main types of digital image representation?  What are the most popular image file formats?  What are the most common types of image processing operations and how do they affect pixel values? By Oge Marques Copyright © 2011 by John Wiley & Sons, Inc. All rights reserved. Digital image representation  Image coordinate convention (not valid for MATLAB!) NB: There is no universally accepted convention or notation. Always check carefully! By Oge Marques Copyright © 2011 by John Wiley & Sons, Inc. All rights reserved. Digital image representation  Mathematical notation By Oge Marques Copyright © 2011 by John Wiley & Sons, Inc. All rights reserved. Digital image representation  MATLAB representation By Oge Marques Copyright © 2011 by John Wiley & Sons, Inc. All rights reserved. Digital image representation  Binary (1-bit) images  2D array, one bit per pixel, a 0 usually means “black” and a 1 means “white”.  In MATLAB: binary images are represented using a logical array of 0s and 1s. By Oge Marques Copyright © 2011 by John Wiley & Sons, Inc. All rights reserved. Digital image representation  Gray-level (8-bit) images  2D array, 8 bits per pixel, a 0 usually means “black” and a 255 means “white”.  In MATLAB: intensity images can be represented using different data types (or classes): uint8, uint16, or double. By Oge Marques Copyright © 2011 by John Wiley & Sons, Inc. All rights reserved. Digital image representation  Color images  RGB representation: each pixel is usually represented by a 24-bit number containing the amount of its Red (R), Green (G), and Blue (B) components  Indexed representation: a 2D array contains indices to a color palette (or look-up table, LUT). By Oge Marques Copyright © 2011 by John Wiley & Sons, Inc. All rights reserved. Digital image representation  24-bit (true color) RGB images By Oge Marques Copyright © 2011 by John Wiley & Sons, Inc. All rights reserved. Digital image representation  Indexed color images By Oge Marques Copyright © 2011 by John Wiley & Sons, Inc. All rights reserved.