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64 lines
1.7 KiB
GLSL
64 lines
1.7 KiB
GLSL
#ifdef GL_ES
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precision mediump float;
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#endif
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uniform sampler2D u_tex0;
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uniform vec2 u_resolution;
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uniform vec2 u_mouse;
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float PI = 3.1415926535897932384626433832795;
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float PI180 = float(PI / 180.0);
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float sind (float a) {
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return sin(a * PI180);
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}
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float cosd (float a) {
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return cos(a * PI180);
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}
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float added (vec2 sh, float sa, float ca, vec2 c, float d) {
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return 0.5 + 0.25 * cos((sh.x * sa + sh.y * ca + c.x) * d) + 0.25 * cos((sh.x * ca - sh.y * sa + c.y) * d);
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}
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void main () {
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float threshold = clamp(0.5, 0.0, 1.0);
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vec2 st = gl_FragCoord.xy/u_resolution.xy;
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if (st.x > 0.5) {
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// Halftone dot matrix shader
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// @author Tomek Augustyn 2010
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// Ported from my old PixelBender experiment
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// https://github.com/og2t/HiSlope/blob/master/src/hislope/pbk/fx/halftone/Halftone.pbk
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float ratio = u_resolution.y / u_resolution.x;
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vec2 dstCoord = vec2(st.x-0.5, st.y*0.5)*2.0;
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vec2 srcCoord = vec2(st.x-0.5, st.y*0.5)*2.0;
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vec2 rotationCenter = vec2(0.5);
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vec2 shift = dstCoord - rotationCenter;
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float dotSize = 5.0;
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float angle = 45.0;
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float rasterPattern = added(shift, sind(angle), cosd(angle), rotationCenter, PI / dotSize * 680.0);
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vec4 srcPixel = texture2D(u_tex0, srcCoord);
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float avg = 0.2125 * srcPixel.r + 0.7154 * srcPixel.g + 0.0721 * srcPixel.b;
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float gray = (rasterPattern * threshold + avg - threshold) / (1.0 - threshold);
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// uncomment to see how the raster pattern looks
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// gray = rasterPattern;
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gl_FragColor = vec4(gray, gray, gray, 1.0);
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} else {
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st = vec2(st.x,st.y*0.5)*2.0;
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gl_FragColor = texture2D(u_tex0, st);
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}
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}
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