Download presentation
Presentation is loading. Please wait.
Published byJanis Sherman Modified over 9 years ago
1
Measurements in Fluid Mechanics 058:180:001 (ME:5180:0001) Time & Location: 2:30P - 3:20P MWF 218 MLH Office Hours: 4:00P – 5:00P MWF 223B-5 HL Instructor: Lichuan Gui lichuan-gui@uiowa.edu http://lcgui.net
2
2 Lecture 24. Digital image & image processing
3
3 Digital image & image processing Digital Image
4
4 Digital image & image processing Digital Image Images constitute a continuous spatial distribution of the irradiance at a plane. Digital images consist of pixels. Each pixel represents a square region of the image on a square grid. Pixel value (gray value) represents intensity of the irradiance – 1-bit: 0 1 – 8-bit: 0 255 –10-bit: 0 1,023 –12-bit: 0 4,095 –24-bit: 0 16,777,215 Bitmap data in file.
5
5 Digital image & image processing Digital Image Sufficient pixels make image look continuous
6
6 Digital image & image processing Digital Image Color models - True color model: (Red,Green,Blue)=(0 255, 0 255, 0 255) - Others: Palettes/look-up table (LUT)/color map/index map/etc.
7
7 Digital image & image processing Digital Image Physical & logical pixels
8
8 Digital image & image processing Digital Image Digital PIV image sample displayed on a PC screen presented as a 2D-function G(x,y)
9
9 Digital image & image processing Digital Image 2D & 3D digital images
10
10 Digital image & image processing Digital Image Histogram (PDF) of digital image PDF – Probability density function
11
11 Digital image & image processing Digital Image Processing Pixel operation Filter operation Many others - Changing gray value of single pixel without considering the neighborhood - Changing gray value of single pixel considering the neighborhood of (2r+1) (2r+1) pixels
12
12 Digital image & image processing Pixel Operation Linear transformation
13
13 Digital image & image processing Pixel Operation Binary operation
14
14 Digital image & image processing Pixel Operation Threshold
15
15 Digital image & image processing Pixel Operation Invert Square Root
16
16 Digital image & image processing Digital Filter Smooth filter
17
17 Digital image & image processing Digital Filter Gradient filter
18
18 Digital image & image processing Digital Filter Laplace filter
19
19 Digital image & image processing Digital Filter Regional normalization
20
20 Digital image & image processing Digital Filter (Removing) unsharp mask
21
21 Digital image & image processing Digital Filter Median Expansion Erosion
22
22 Digital image & image processing Digital image files Device independent image files Device dependent image files - Microsoft Windows Bitmap “*.bmp” - Tag Image File Format “*.tif” - Graphics Interchange Format “*.gif” - JPEG File Interchange Format “*.jpg” - Many others - Raw image formats (e.g. *.raww) - TSI image file Format “*.img” - DANTEC image file format “*.img” - LAVISION image file format “*.img” - Others Basic components of a digital image Information in a bitmap header - Header, Palette, Bitmap Data, Footer etc. –File Identifier –File Version –Number of Lines per Image –Number of Pixels per Line –Number of Bits per Pixel –Number of Color Planes –Compression Type –X & Y Origin of Image –Text Description –Others –Unused Space
23
23 Digital image & image processing Digital image files Microsoft Windows Bitmap –14-byte file header (Version 2.x +) Byte 1 2File type, always 4D42h (“BM”); Byte 3 6Size of the file in bytes; Byte 7 8Reserved 1, always 0; Byte 9 10Reserved 2, always 0; Byte 11 14Starting position of image data in bytes. –Bitmap header Byte 1 4Size of this header in bits; Byte 5 8Image width in pixels;(2 bytes for version 2.x) Byte 9 12Image height in pixels; (2 bytes for version 2.x) Byte 13 14Number of color planes; Byte 15 16Number of bits per pixel; (end of version 2.x) Byte 17 20Compression methods used; Byte 21 24Size of bitmap in Bytes; Byte 25 28Horizontal resolution in pixels per meter; Byte 29 32Vertical resolution in pixels per meter; Byte 33 36Number of colors in the image; Byte 37 40Minimum number of important colors. (end of version 3.x) Up to 108 bytes for Version 4.x –Color Palette One-, 4-, and 8-bit BMP files always contain a color palette 24-bit BMP files never contain color palettes
24
24 Digital image & image processing Project warm-up Write a Matlab program to read gray values at the center and 4 corners of image: http://lcgui.net/lectures/lecture02/image01.bmp Try to use pixel or filter operations to process the digital image –A 124×124-pixel uncompressed 8-bit gray-scale BMP file File header:14 bytes Bitmap header:40 bytes Color palette:1024 bytes Bitmap data:15376 bytes Total size:16454bytes –Simplest Matlab program A=imread('image01.bmp'); A(1,1) A(1,124) A(124,1) A(124,124) A(62,62) imshow(A);
Similar presentations
© 2025 SlidePlayer.com. Inc.
All rights reserved.