1 /*

2 Printblobs - typography display hack

3 Copyright (C) 2013 John Tsiombikas <nuclear@member.fsf.org>

4

5 This program is free software: you can redistribute it and/or modify

6 it under the terms of the GNU General Public License as published by

7 the Free Software Foundation, either version 3 of the License, or

8 (at your option) any later version.

9

10 This program is distributed in the hope that it will be useful,

11 but WITHOUT ANY WARRANTY; without even the implied warranty of

12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the

13 GNU General Public License for more details.

14

15 You should have received a copy of the GNU General Public License

16 along with this program. If not, see <http://www.gnu.org/licenses/>.

17 */

18 uniform sampler2D framebuf, dither_tex;

19 uniform int dither_levels, dither_size;

20

21 uniform float tfadein;

22

23 vec4 fetch_pixel(vec2 texcoord)

24 {

25 float x = step(0.5, mod(texcoord.y, 0.5) / 0.5);

26 float offs = mix(1.0 - tfadein, tfadein - 1.0, x);

27 vec2 tc = texcoord + vec2(offs, 0.0);

28

29 return (1.0 - step(1.0, tc.x)) * step(0.0, tc.x) * texture2D(framebuf, tc);

30 }

31

32 void main()

33 {

34 float levels = float(dither_levels);

35

36 //vec4 pixel = texture2D(framebuf, gl_TexCoord[0].xy);

37 vec4 pixel = fetch_pixel(gl_TexCoord[0].xy);

38 float lum = dot(pixel.xyz, vec3(0.2126, 0.7152, 0.0722));

39 float coord_shift = floor(lum * levels) / levels;

40

41 vec2 dsz2 = vec2(float(dither_size), float(dither_size));

42

43 vec2 coord = mod(gl_FragCoord.xy, dsz2) / float(dither_size);

44 coord.y = coord.y / levels + coord_shift;

45 float val = texture2D(dither_tex, coord).x;

46

47 const vec3 dark_col = vec3(0.043, 0.286, 0.337);

48 const vec3 bright_col = vec3(0.965, 0.778, 0.555);

49

50 gl_FragColor = vec4(mix(dark_col, bright_col, val), 1.0);

51 }