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Tutorial # 9 – Q#6.16 from textbook
Nov. 21, 2013
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The following 8-bit images are (left to right) the H, S and I component images from Fig.6.16. The numbers indicate gray-level values. Answer the following questions, explaining the basis for your answer in each. If it is not possible to answer a question based on the given information, state why you cannot do so.
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85
43
0
128
255
170
85
A) Hue B) Saturation C) Intensity
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A)Give the gray-level values of all regions in the hue image.
85
43
0
128
A) Hue
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HSI Model
http://en.wikipedia.org/wiki/File:HSV_color_solid_cone_chroma_gray.png
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Hue A colour attribute that describes a pure colour Hue refers to an angle where red = 0 But recall that the hue image is 8-bit meaning
that there is a maximum of 2^8 = 256 values/angles
85
43
0
128
Need to find Magenta, Blue and White
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Blue 240 In 8-bits
Magenta
White Equal proportions of Red, Blue and Green so its hue
is zero Black
No proportions of Red, Blue and Green, so its hue is also zero
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B) Give the gray-level value of all regions in the saturation image.
255
B) Saturation
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Saturation Gives a measure of the degree to which a
pure colour is diluted by white light “The colourfulness of a stimulus relative to its
own brightness” (Wiki article)
http://en.wikipedia.org/wiki/File:HSV_color_solid_cone_chroma_gray.png
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The colours are spectrum colours – they are fully saturated.
255 applies to all colour regions Center of the circle is white, so saturation is 0
255
B) Saturation
0
255
255
255 255
255
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C) Give the gray-level values of all regions in the intensity image.
170
85
C) Intensity
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Intensity Brightness, lightness
“Attribute of a visual sensation according to which an area appears to emit more or less light”
“Amount of light passing through a particular area
http://en.wikipedia.org/wiki/File:HSV_color_solid_cone_chroma_gray.png
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Center region (white) has equal intensities of fully saturated red, green and blue
Primary colour regions have only one fully saturated colour– has a value of 85 Similar for other regions
Secondary colour regions have two fully saturated colours – has a value of 170 (85 x 2) Similar for other regions
Therefore center has three – (85 x 3 = 255)
Black regions have none – 0
170
85
C) Intensity
170
17085
85
255
0
