Producing images
Draw a segment with Bresenham, filter by convolution (blur, sharpen, edges), threshold with the histogram, composite two layers with the alpha channel, generate a texture from noise.
- 27 cards
- 5 topics
- Free
The outline, topic by topic
Each topic is weighted the way the exam weighs it.
- Concepts
- Questions
- Sort and link
- The numbers
- The curves
A few cards from the deck
Bresenham's algorithm: what is it?
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A method that picks a segment's pixels using only integer additions and comparisons, tracking the gap from the ideal line.
With no floats or divisions, it is very fast. At each step in x it decides whether y stays or moves one step, based on the accumulated error.
The horizontal Sobel kernel, with rows (−1, 0, 1), (−2, 0, 2), (−1, 0, 1), is laid over this grey neighbourhood: each value is multiplied by the weight in the same place, then everything is added up. What is the result for the central pixel?
```text
10 10 50
10 10 50
10 10 50`- 160
- 40
- 0
- −160
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160
Top row: −10 + 0 + 50 = 40; middle row: −20 + 0 + 100 = 80; bottom row: 40. Total: 160. The result is strongly positive: there is a strong vertical edge, dark on the left to light on the right. With the light side on the left and the dark side on the right, you would get −160.
The … operator uses two 3 × 3 kernels, one horizontal and one vertical, whose weights sum to …: it responds strongly to edges and stays at zero on flat areas.
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The Sobel operator uses two 3 × 3 kernels, one horizontal and one vertical, whose weights sum to 0: it responds strongly to edges and stays at zero on flat areas.
The horizontal kernel measures the difference between the right and left columns. Edge strength combines both results: the square root of (Gx² + Gy²).