bresenham

Bresenham algorithm and mlx library 🚧 under development 🚧

On this Project, You will note the window->img size is assigned to the map_info->img_wide and map_info->img_high function.

This changes the size will affect at bpp and the size of the image, but not the size of the window.

How This happens:

Imagine that if we use a window size of 800 * 600:

bpp = 800*600*4 = 32000
size_line = 32000/4 = 800

If we want to use an image size of 300 * 300:

bpp = 300*300*4 = 120000
size_line = 120000/4 = 300

OK, I think now it's clear for you that the size of the image is not the size of the window.

Let us now see how the Bresenham algorithm works.

0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0
0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0
0  0  1  1  0  0  1  1  0  0  0  1  1  1  1  1  0  0  0
0  0  1  1  0  0  1  1  0  0  0  0  0  0  0  1  1  0  0
0  0  1  1  0  0  1  1  0  0  0  0  0  0  0  1  1  0  0
0  0  1  1  1  1  1  1  0  0  0  0  1  1  1  1  0  0  0
0  0  0  1  1  1  1  1  0  0  0  1  1  0  0  0  0  0  0
0  0  0  0  0  0  1  1  0  0  0  1  1  0  0  0  0  0  0
0  0  0  0  0  0  1  1  0  0  0  1  1  1  1  1  1  0  0
0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0
0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0

1: is Cube 0: is Empty

Cube is the pixel that is going to be drawn.

For each, 1 will be

(x0, y0)--(dx)--(x1, y0)
 |                     
 |                     
(dy)                   
 |                     
 |                     
(x0, y1)--(dx)--(x1, y1)

dy: is the difference between the y0 and y1. dx: is the difference between the x0 and x1.

OK, Now if check map, the first 1 at array will be on (3, 3).

what is locations for (3, 3) on pixel?

We need to get dx and dy

• Step One:
  • img_wide = 300 and img_high = 300.
  • each 4 bytes is a pixel.
  • pixels = img_wide * img_high * 4 = 300 * 300 * 4 = 360000
  • pixels / 4 = 360000 / 4 = 90000
  • that's means we will use 90000 pixels each one have 4 bytes.

Now have, 90000 pixels to draw map size is (18, 10).

• Step two:
  • dx = img_wide \ map_wide = 300 / 18 = 16.6
  • dy = img_high \ map_high = 300 / 10 = 30.0

OK now we know x0 to x1 will be x0 + dx and locations for (3, 3) will be (3dx, 3dy).

(3, 3) -> pixel = (3*dx, 3*dy) = (3 * 16, 3 * 30.0) = (48, 90)

Now I have pixel location is (48, 90).

To draw at window->data

window->data[90*window->img_wide + 48] = 0xffffffff;