From 9d3cdc7f5ee96c3b2a9342e44b62102f5b05be3b Mon Sep 17 00:00:00 2001
From: Matthias Schiffer <mschiffer@universe-factory.net>
Date: Mon, 1 Feb 2016 14:03:21 +0100
Subject: Add glslwrite tool and some examples

---
 glslwrite.c | 204 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 204 insertions(+)
 create mode 100644 glslwrite.c

(limited to 'glslwrite.c')

diff --git a/glslwrite.c b/glslwrite.c
new file mode 100644
index 0000000..ebe81d4
--- /dev/null
+++ b/glslwrite.c
@@ -0,0 +1,204 @@
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <unistd.h>
+
+#include <png.h>
+
+#include <GL/glew.h>
+
+#include <SDL2/SDL.h>
+#include <SDL2/SDL_opengl.h>
+
+
+
+static unsigned frame_time = 0;
+
+
+static GLint time_loc;
+static GLint res_loc;
+
+
+static char * readfile(const char *filename) {
+        FILE *f = fopen(filename, "r");
+        if (!f)
+                return NULL;
+
+        size_t size = 1024;
+        char *buffer = malloc(size+1);
+        size_t count = 0, r;
+
+        do {
+                if (count == size) {
+                        size *= 2;
+                        buffer = realloc(buffer, size+1);
+                }
+
+                r = fread(buffer+count, 1, size-count, f);
+                count += r;
+        } while (r);
+
+        fclose(f);
+
+        buffer[count] = 0;
+
+        return buffer;
+}
+
+static void printShaderInfoLog(GLuint obj) {
+        GLint length = 0;
+
+        glGetShaderiv(obj, GL_INFO_LOG_LENGTH, &length);
+
+        if(length > 0) {
+                char log[length];
+
+                glGetShaderInfoLog(obj, sizeof(log), NULL, log);
+                fprintf(stderr, "%s\n", log);
+        }
+}
+
+static void printProgramInfoLog(GLuint obj) {
+        GLint length = 0;
+
+        glGetProgramiv(obj, GL_INFO_LOG_LENGTH, &length);
+
+        if(length > 0) {
+                char log[length];
+
+                glGetProgramInfoLog(obj, sizeof(log), NULL, log);
+                fprintf(stderr, "%s\n", log);
+        }
+}
+
+static void init(char *filename) {
+        glewInit();
+
+	glDisable(GL_DEPTH_TEST);
+
+        char *shader = readfile(filename);
+        if (!shader) {
+                fprintf(stderr, "Error: unable to read '%s'\n", filename);
+                exit(1);
+        }
+
+        GLuint frag = glCreateShader(GL_FRAGMENT_SHADER);
+        glShaderSource(frag, 1, (const GLchar **)&shader, NULL);
+        glCompileShader(frag);
+        printShaderInfoLog(frag);
+
+        GLuint program = glCreateProgram();
+        glAttachShader(program, frag);
+
+        glLinkProgram(program);
+        printProgramInfoLog(program);
+
+        glBindFragDataLocation(program, 0, "fragColor");
+        time_loc = glGetUniformLocation(program, "time");
+        res_loc = glGetUniformLocation(program, "res");
+
+        glUseProgram(program);
+}
+
+static void savePNG(uint8_t *pixels, int width, int height, const char *output_dir) {
+        char filename[strlen(output_dir) + 20];
+        snprintf(filename, sizeof(filename), "%s/%010u.png", output_dir, frame_time);
+
+        FILE *f = fopen(filename, "wb");
+	if (!f) {
+                fprintf(stderr, "unable to open PNG file\n");
+                exit(1);
+        }
+
+	png_structp png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
+	if (!png_ptr) {
+                fprintf(stderr, "unable to open PNG file\n");
+                exit(1);
+        }
+
+        png_set_swap_alpha(png_ptr);
+
+	png_infop info_ptr = png_create_info_struct(png_ptr);
+	if (!info_ptr) {
+		fprintf(stderr, "unable to create PNG info struct\n");
+                exit(1);
+	}
+
+	if (setjmp(png_jmpbuf(png_ptr))) {
+		fprintf(stderr, "unable to write PNG file\n");
+                exit(1);
+	}
+
+	png_init_io(png_ptr, f);
+
+	png_set_IHDR(png_ptr, info_ptr, width, height, 8, PNG_COLOR_TYPE_RGB_ALPHA,
+		     PNG_INTERLACE_NONE, PNG_COMPRESSION_TYPE_DEFAULT, PNG_FILTER_TYPE_DEFAULT);
+
+	uint8_t *row_pointers[height];
+	for (size_t i = 0; i < height; i++)
+		row_pointers[i] = &pixels[4*i*width];
+
+	png_set_rows(png_ptr, info_ptr, row_pointers);
+	png_write_png(png_ptr, info_ptr, PNG_TRANSFORM_IDENTITY, NULL);
+
+	png_destroy_write_struct(&png_ptr, &info_ptr);
+	fclose(f);
+}
+
+static void render(SDL_Window *window, const char *output_dir) {
+        int width, height;
+        SDL_GetWindowSize(window, &width, &height);
+
+	glViewport(0, 0, (GLsizei)width, (GLsizei)height);
+
+        glUniform1f(time_loc, frame_time);
+        glUniform2f(res_loc, width, height);
+
+	glBegin(GL_QUADS);
+	glVertex2f(-1, -1);
+	glVertex2f(1, -1);
+	glVertex2f(1, 1);
+	glVertex2f(-1, 1);
+	glEnd();
+
+	SDL_GL_SwapWindow(window);
+
+        uint8_t pixels[width*height*4];
+        glReadPixels(0, 0, width, height, GL_RGBA, GL_UNSIGNED_INT_8_8_8_8, pixels);
+        savePNG(pixels, width, height, output_dir);
+
+        frame_time += 20;
+}
+
+
+int main(int argc, char *argv[]) {
+	bool running = true;
+
+        if (argc != 3) {
+                fprintf(stderr, "Usage: glslwrite <shader> <output directory>\n");
+                exit(1);
+        }
+
+	SDL_Init(SDL_INIT_VIDEO);
+
+	SDL_Window *window = SDL_CreateWindow("glslwrite", 0, 0, 800, 800, SDL_WINDOW_OPENGL|SDL_WINDOW_RESIZABLE);
+        SDL_GL_CreateContext(window);
+
+        init(argv[1]);
+
+	while (running) {
+		SDL_Event e;
+
+		while( SDL_PollEvent(&e)) {
+			if(e.type == SDL_QUIT) {
+				running = false;
+                                break;
+			}
+		}
+
+		render(window, argv[2]);
+                //usleep(1);
+	}
+
+	return 0;
+}
-- 
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