IAT455 Computational Media Assignment 1
How to submit: Submit through canvas only.
Late assignment policy: The mark for a late assignment will be marked down 25% for each day it is late.
Q1: (2 pts)
Late assignment policy: The mark for a late assignment will be marked down 25% for each day it is late.
Q1: (2 pts)
Suppose you wish to create a wavy effect, as in the figure below. This effect comes from replacing the image x value by an x value offset by a small amount. Suppose the image size is 160 rows x 120 columns of pixels. Make the maximum shift in x equal to 16 pixels. Write an expression that would show this transformation and justify your choice of expression.
Q2: (2 pts)
Suppose we decide to quantize an 8-bit grayscale image down to just 2 bits of accuracy. What is the simplest way to do so? What ranges of byte values in the original image are mapped to what quantized values?
Q3: (3 pts)
Consider a screen containing plain black text on a solid white background. There will be many long runs of white pixels in the blank space, and many short runs of black pixels within the text. Let us take a hypothetical single scan line, with 0 representing a black pixel and 1 representing white:
Suppose we decide to quantize an 8-bit grayscale image down to just 2 bits of accuracy. What is the simplest way to do so? What ranges of byte values in the original image are mapped to what quantized values?
Q3: (3 pts)
Consider a screen containing plain black text on a solid white background. There will be many long runs of white pixels in the blank space, and many short runs of black pixels within the text. Let us take a hypothetical single scan line, with 0 representing a black pixel and 1 representing white:
IAT455 Computational Media
111111111 111000111111111 1100001111111111111111111110011111111111
Explain how you would implement the run-length encoding on this scan line. What compression
ratio would you achieve?
Q4: (3 pts)
a) What is the meaning of the pre-multiplied (R, G, B, A) set (0.0, 0.25, 0.25, 0.5)?
b) Representing colors as pre-multiplied (R, G, B, A) sets, what color do we get if we composite (0.0, 0.25, 0.25, 0.5) OVER (1.0, 0.0, 1.0, 1.0)?
Q5: (Code) (10 points)
Create a composite image of yourself and a famous place of your choice. Start with an image of yourself, taken on a background containing a limited range of hue (similar to Figure 6.29 in your textbook). Write code to extract a matte from this image using the 'Keying based on chrominance' method, as explained in class and in your textbook. Then, using the matte, produce the composite of yourself and the famous place.
111111111 111000111111111 1100001111111111111111111110011111111111
Explain how you would implement the run-length encoding on this scan line. What compression
ratio would you achieve?
Q4: (3 pts)
a) What is the meaning of the pre-multiplied (R, G, B, A) set (0.0, 0.25, 0.25, 0.5)?
b) Representing colors as pre-multiplied (R, G, B, A) sets, what color do we get if we composite (0.0, 0.25, 0.25, 0.5) OVER (1.0, 0.0, 1.0, 1.0)?
Q5: (Code) (10 points)
Create a composite image of yourself and a famous place of your choice. Start with an image of yourself, taken on a background containing a limited range of hue (similar to Figure 6.29 in your textbook). Write code to extract a matte from this image using the 'Keying based on chrominance' method, as explained in class and in your textbook. Then, using the matte, produce the composite of yourself and the famous place.
Output from your code should show:
- original image, captured by camera, with background of limited range of hues
- image of famous place that you will use in your composite
- the matte image obtained through the Keying based on chrominance' method
- intermediate images (if there are any)
- final composite result
The code should have explanatory comments and should be submitted in zip format, as project exported from Eclipse. Name your project in this format: Firstnamel .astNameA1 (for example: JohnSmithA1).
Additionally, submit a report in which you explain your process step by step and the challenges o difficulties you have encountered. Analyze your final composite and explain any artifacts that are present (areas of incorrect color, transparency, etc).
- original image, captured by camera, with background of limited range of hues
- image of famous place that you will use in your composite
- the matte image obtained through the Keying based on chrominance' method
- intermediate images (if there are any)
- final composite result
The code should have explanatory comments and should be submitted in zip format, as project exported from Eclipse. Name your project in this format: Firstnamel .astNameA1 (for example: JohnSmithA1).
Additionally, submit a report in which you explain your process step by step and the challenges o difficulties you have encountered. Analyze your final composite and explain any artifacts that are present (areas of incorrect color, transparency, etc).
2020-02-03