Color Image Processing

Image Processing CSE 166 Lecture 9 Reading

• Processing, 4th edition – Chapter 7: Image Processing

CSE 166, Fall 2017 2

CSE 166, Fall 2017 3 Separating visible

CSE 166, Fall 2017 4 Human eye cones

CSE 166, Fall 2017 5 Note that Mixing light , , and are not accurate in the Light book. More accurate colors below. Primary and secondary colors are swapped

GREEN Pigment CYAN

BLUE

MAGENTA

CSE 166, Fall 2017 6 RGB

RGB color cube RGB coordinates

CSE 166, Fall 2017 7 XYZ color model and coordinates

Not actual colors locations; just gives an idea

CSE 166, Fall 2017 8 Color

Average person

Computer monitor

Printer

CSE 166, Fall 2017 9 HSI color model: Relationship to RGB color model

All colors with cyan RGB color cube rotated such that line joining and (intensity axis) is vertical

CSE 166, Fall 2017 10 HSI color model RGB color cube rotated such that HSI intensity axis observer is on intensity axis, beyond white looking towards black RGB color cube

Shape does not matter, only angle from red CSE 166, Fall 2017 11 HSI color model

HS‐plane is orthogonal to intensity axis

CSE 166, Fall 2017 12 Color models

CMYK

CMY

RGB

HSI

CSE 166, Fall 2017 13 Intensity slicing

Grayscale to 2 colors

CSE 166, Fall 2017 14 Intensity slicing

Grayscale to 2 colors

CSE 166, Fall 2017 15 Intensity slicing

Grayscale to 8 colors

CSE 166, Fall 2017 16 Intensity slicing

Colorbar

Grayscale to 256 colors CSE 166, Fall 2017 17 Intensity to color transformations

Grayscale RGB input image output image

CSE 166, Fall 2017 18 Intensity to color transformations X‐ray grayscale input image

Without With explosive explosive

RGB output images

Misses CSE 166, Fall 2017 explosive 19 Intensity to color transformations

Multiple Single grayscale RGB input images output image

CSE 166, Fall 2017 20 Intensity to color transformations Red (R) Green (G) Blue (B)

Multiple satellite grayscale input images

Near (NIR) NIR,G,B as RGB R,NIR,B as RGB Output RGB images 21 Intensity to color transformations

Multiple grayscale Single input images, RGB some outside of output image

Physical and chemical processes likely to Close up affect sensor response

CSE 166, Fall 2017 22 Full‐ processing

Spatial filtering: process each independently

CSE 166, Fall 2017 23 Full‐color image processing Spatial filtering: image smoothing

All RGB HSI intensity Difference channels channel only

CSE 166, Fall 2017 24 Full‐color image processing Spatial filtering: image sharpening

All RGB HSI intensity Difference channels channel only

CSE 166, Fall 2017 25 Full‐color image processing : do not process each channel independently

1. RGB to HSI 2. Histogram 4. HSI saturation equalize adjustment HSI intensity 3. HSI to RGB

CSE 166, Fall 2017 26