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/**
* Draw a series of textured quads after each quad, use glTexSubImage()
* to change one row of the texture image.
*/
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <glad/glad.h>
#include "glut_wrap.h"
static GLint Win = 0;
static GLuint Tex = 0;
static void Init(void)
{
fprintf(stderr, "GL_RENDERER = %s\n", (char *) glGetString(GL_RENDERER));
fflush(stderr);
glGenTextures(1, &Tex);
glBindTexture(GL_TEXTURE_2D, Tex);
glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
}
static void Reshape(int width, int height)
{
float ar = (float) width / height;
glViewport(0, 0, width, height);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(-ar, ar, -1.0, 1.0, -1.0, 1.0);
glMatrixMode(GL_MODELVIEW);
}
static void Key(unsigned char key, int x, int y)
{
if (key == 27) {
glDeleteTextures(1, &Tex);
glutDestroyWindow(Win);
exit(1);
}
glutPostRedisplay();
}
static void Draw(void)
{
GLubyte tex[16][16][4];
GLubyte row[16][4];
int i, j;
for (i = 0; i < 16; i++) {
for (j = 0; j < 16; j++) {
if ((i + j) & 1) {
tex[i][j][0] = 128;
tex[i][j][1] = 128;
tex[i][j][2] = 128;
tex[i][j][3] = 255;
}
else {
tex[i][j][0] = 255;
tex[i][j][1] = 255;
tex[i][j][2] = 255;
tex[i][j][3] = 255;
}
}
}
for (i = 0; i < 16; i++) {
row[i][0] = 255;
row[i][1] = 0;
row[i][2] = 0;
row[i][3] = 255;
}
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, 16, 16, 0,
GL_RGBA, GL_UNSIGNED_BYTE, tex);
glEnable(GL_TEXTURE_2D);
glClear(GL_COLOR_BUFFER_BIT);
for (i = 0; i < 9; i++) {
glPushMatrix();
glTranslatef(-4.0 + i, 0, 0);
glScalef(0.5, 0.5, 1.0);
glBegin(GL_QUADS);
glTexCoord2f(1,0);
glVertex3f( 0.9, -0.9, 0.0);
glTexCoord2f(1,1);
glVertex3f( 0.9, 0.9, 0.0);
glTexCoord2f(0,1);
glVertex3f(-0.9, 0.9, 0.0);
glTexCoord2f(0,0);
glVertex3f(-0.9, -0.9, 0.0);
glEnd();
glPopMatrix();
/* replace a row of the texture image with red texels */
if (i * 2 < 16)
glTexSubImage2D(GL_TEXTURE_2D, 0, 0, i*2, 16, 1,
GL_RGBA, GL_UNSIGNED_BYTE, row);
}
glutSwapBuffers();
}
int main(int argc, char **argv)
{
glutInit(&argc, argv);
glutInitWindowSize(900, 200);
glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE);
Win = glutCreateWindow(*argv);
if (!Win) {
exit(1);
}
gladLoadGL();
Init();
glutReshapeFunc(Reshape);
glutKeyboardFunc(Key);
glutDisplayFunc(Draw);
glutMainLoop();
return 0;
}
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