From a433565494bbe4da7eb4596d2c8c132cd42d3ba9 Mon Sep 17 00:00:00 2001
From: Szabolcs Dombi <szabolcs@szabolcsdombi.com>
Date: Fri, 26 Jan 2024 17:42:28 +0200
Subject: [PATCH] pygame postprocessing shader

---
 examples/pygame/postprocessing.py | 170 ++++++++++++++++++++++++++++++
 1 file changed, 170 insertions(+)
 create mode 100644 examples/pygame/postprocessing.py

diff --git a/examples/pygame/postprocessing.py b/examples/pygame/postprocessing.py
new file mode 100644
index 00000000..2cb6a386
--- /dev/null
+++ b/examples/pygame/postprocessing.py
@@ -0,0 +1,170 @@
+import random
+import struct
+
+import pygame
+import zengl
+
+pygame.init()
+pygame.display.set_mode((640, 480), flags=pygame.OPENGL | pygame.DOUBLEBUF)
+screen = pygame.surface.Surface((320, 240))
+
+ctx = zengl.context()
+image = ctx.image((320, 240), "rgba8unorm")
+pipeline = ctx.pipeline(
+    vertex_shader="""
+        #version 300 es
+        precision highp float;
+
+        vec2 vertices[4] = vec2[](
+            vec2(-1.0, -1.0),
+            vec2(-1.0, 1.0),
+            vec2(1.0, -1.0),
+            vec2(1.0, 1.0)
+        );
+
+        out vec2 vertex;
+
+        void main() {
+            gl_Position = vec4(vertices[gl_VertexID], 0.0, 1.0);
+            vertex = vertices[gl_VertexID];
+        }
+    """,
+    fragment_shader="""
+        #version 300 es
+        precision highp float;
+
+        uniform float time;
+        uniform vec2 screen_size;
+        uniform sampler2D Texture;
+
+        in vec2 vertex;
+        out vec4 out_color;
+
+        float hash13(vec3 p3) {
+            p3 = fract(p3 * 0.1031);
+            p3 += dot(p3, p3.zyx + 31.32);
+            return fract((p3.x + p3.y) * p3.z);
+        }
+
+        vec2 hash23(vec3 p3) {
+            p3 = fract(p3 * vec3(0.1031, 0.1030, 0.0973));
+            p3 += dot(p3, p3.yzx + 33.33);
+            return fract((p3.xx + p3.yz) * p3.zy);
+        }
+
+        vec3 sample_screen(vec2 uv) {
+            return vec3(
+                texture(Texture, uv - vec2(0.002, 0.0)).r,
+                texture(Texture, uv).g,
+                texture(Texture, uv + vec2(0.002, 0.0)).b
+            );
+        }
+
+        vec3 screen(vec2 vertex) {
+            if (abs(vertex.x) > 1.001 || abs(vertex.y) > 1.001) {
+                return vec3(0.0);
+            }
+            vec2 uv = vertex * 0.5 + 0.5;
+            vec3 color = sample_screen(uv);
+            float noise = hash13(floor(vec3(uv * screen_size, floor(time))));
+            float scanline = sin(uv.y * screen_size.y * 3.141592 + time * 0.05) * 0.1 + 0.9;
+            color *= 1.0 + (noise - 0.5) * 0.1;
+            color = color * scanline * 1.05 + 0.05;
+            return color;
+        }
+
+        void main() {
+            vec2 v = vertex * (1.0 + pow(abs(vertex.yx), vec2(2.0)) * 0.1);
+            vec3 color = vec3(0.0);
+            for (int i = 0; i < 16; ++i) {
+                vec2 offset = hash23(vec3(v * screen_size, float(i))) - 0.5;
+                color += screen(v * 1.01 + offset / screen_size);
+            }
+            color /= 16.0;
+            out_color = vec4(color, 1.0);
+        }
+    """,
+    layout=[
+        {
+            "name": "Texture",
+            "binding": 0,
+        },
+    ],
+    resources=[
+        {
+            "type": "sampler",
+            "binding": 0,
+            "image": image,
+            "min_filter": "nearest",
+            "mag_filter": "nearest",
+            "wrap_x": "clamp_to_edge",
+            "wrap_y": "clamp_to_edge",
+        },
+    ],
+    uniforms={
+        "time": 0.0,
+        "screen_size": (320.0, 240.0),
+    },
+    framebuffer=None,
+    viewport=(0, 0, 640, 480),
+    topology="triangle_strip",
+    vertex_count=4,
+)
+
+
+def make_square(size, color):
+    surface = pygame.surface.Surface((size, size), pygame.SRCALPHA)
+    surface.fill(color)
+    return surface
+
+
+squares = []
+for _ in range(20):
+    size = random.randint(20, 80)
+    color = (random.randint(0, 255), random.randint(0, 255), random.randint(0, 255))
+    square = make_square(size, color)
+    squares.append({
+        "position": (random.randint(0, 320), random.randint(0, 240)),
+        "rotation": random.randint(0, 360),
+        "surface": square,
+    })
+
+
+clock = pygame.Clock()
+
+space_down = False
+
+while True:
+    for event in pygame.event.get():
+        if event.type == pygame.QUIT:
+            pygame.quit()
+            quit()
+
+        if event.type in (pygame.KEYDOWN, pygame.KEYUP) and event.key == pygame.K_SPACE:
+                space_down = event.type == pygame.KEYDOWN
+
+    screen.fill((0, 0, 0))
+
+    for square in squares:
+        square["rotation"] += 1
+        if square["rotation"] > 360:
+            square["rotation"] = 0
+        rotated_surface = pygame.transform.rotate(square["surface"], square["rotation"])
+        width, height = rotated_surface.get_size()
+        position = (square["position"][0] - width // 2, square["position"][1] - height // 2)
+        screen.blit(rotated_surface, position)
+
+    ctx.new_frame()
+    image.write(pygame.image.tobytes(screen, "RGBA", flipped=True))
+
+    if not space_down:
+        pipeline.uniforms["time"][:] = struct.pack("f", pygame.time.get_ticks())
+        pipeline.render()
+
+    else:
+        image.blit(size=(640, 480))
+
+    ctx.end_frame()
+
+    pygame.display.flip()
+    clock.tick(60)