1 /**
2 * glCopyPixels test
3 *
4 * Brian Paul
5 * 14 Sep 2007
6 */
7
8
9 #include <stdio.h>
10 #include <stdlib.h>
11 #include <string.h>
12 #include <glad/glad.h>
13 #include "glut_wrap.h"
14
15 #include "readtex.h"
16
17 #define IMAGE_FILE DEMOS_DATA_DIR "arch.rgb"
18
19 static int ImgWidth, ImgHeight;
20 static GLenum ImgFormat;
21 static GLubyte *Image = NULL;
22
23 static int WinWidth = 800, WinHeight = 800;
24 static int Xpos, Ypos;
25 static int Scissor = 0;
26 static float Xzoom, Yzoom;
27 static GLboolean DrawFront = GL_FALSE;
28 static GLboolean Dither = GL_TRUE;
29 static GLboolean Invert = GL_FALSE;
30
31
Reset(void)32 static void Reset( void )
33 {
34 Xpos = Ypos = 20;
35 Scissor = 0;
36 Xzoom = Yzoom = 1.0;
37 }
38
39
Display(void)40 static void Display( void )
41 {
42 const int dx = (WinWidth - ImgWidth) / 2;
43 const int dy = (WinHeight - ImgHeight) / 2;
44
45 if (DrawFront) {
46 glDrawBuffer(GL_FRONT);
47 glReadBuffer(GL_FRONT);
48 }
49 else {
50 glDrawBuffer(GL_BACK);
51 glReadBuffer(GL_BACK);
52 }
53
54 glClear( GL_COLOR_BUFFER_BIT );
55
56 /* draw original image */
57 glWindowPos2iARB(dx, dy);
58 glDrawPixels(ImgWidth, ImgHeight, ImgFormat, GL_UNSIGNED_BYTE, Image);
59
60 if (Scissor)
61 glEnable(GL_SCISSOR_TEST);
62
63 if (Invert) {
64 glPixelTransferf(GL_RED_SCALE, -1.0);
65 glPixelTransferf(GL_GREEN_SCALE, -1.0);
66 glPixelTransferf(GL_BLUE_SCALE, -1.0);
67 glPixelTransferf(GL_RED_BIAS, 1.0);
68 glPixelTransferf(GL_GREEN_BIAS, 1.0);
69 glPixelTransferf(GL_BLUE_BIAS, 1.0);
70 }
71
72 /* draw copy */
73 glPixelZoom(Xzoom, Yzoom);
74 glWindowPos2iARB(Xpos, Ypos);
75 glCopyPixels(dx, dy, ImgWidth, ImgHeight, GL_COLOR);
76 glPixelZoom(1, 1);
77
78 glDisable(GL_SCISSOR_TEST);
79
80 if (Invert) {
81 glPixelTransferf(GL_RED_SCALE, 1.0);
82 glPixelTransferf(GL_GREEN_SCALE, 1.0);
83 glPixelTransferf(GL_BLUE_SCALE, 1.0);
84 glPixelTransferf(GL_RED_BIAS, 0.0);
85 glPixelTransferf(GL_GREEN_BIAS, 0.0);
86 glPixelTransferf(GL_BLUE_BIAS, 0.0);
87 }
88
89 if (DrawFront)
90 glFinish();
91 else
92 glutSwapBuffers();
93 }
94
95
Reshape(int width,int height)96 static void Reshape( int width, int height )
97 {
98 WinWidth = width;
99 WinHeight = height;
100
101 glViewport( 0, 0, width, height );
102 glMatrixMode( GL_PROJECTION );
103 glLoadIdentity();
104 glOrtho( 0.0, width, 0.0, height, 0.0, 2.0 );
105 glMatrixMode( GL_MODELVIEW );
106 glLoadIdentity();
107
108 glScissor(width/4, height/4, width/2, height/2);
109 }
110
111
Key(unsigned char key,int x,int y)112 static void Key( unsigned char key, int x, int y )
113 {
114 (void) x;
115 (void) y;
116 switch (key) {
117 case ' ':
118 Reset();
119 break;
120 case 'd':
121 Dither = !Dither;
122 if (Dither)
123 glEnable(GL_DITHER);
124 else
125 glDisable(GL_DITHER);
126 break;
127 case 'i':
128 Invert = !Invert;
129 break;
130 case 's':
131 Scissor = !Scissor;
132 break;
133 case 'x':
134 Xzoom -= 0.1;
135 break;
136 case 'X':
137 Xzoom += 0.1;
138 break;
139 case 'y':
140 Yzoom -= 0.1;
141 break;
142 case 'Y':
143 Yzoom += 0.1;
144 break;
145 case 'f':
146 DrawFront = !DrawFront;
147 printf("glDrawBuffer(%s)\n", DrawFront ? "GL_FRONT" : "GL_BACK");
148 break;
149 case 27:
150 exit(0);
151 break;
152 }
153 glutPostRedisplay();
154 }
155
156
SpecialKey(int key,int x,int y)157 static void SpecialKey( int key, int x, int y )
158 {
159 const int step = (glutGetModifiers() & GLUT_ACTIVE_SHIFT) ? 10 : 1;
160 (void) x;
161 (void) y;
162 switch (key) {
163 case GLUT_KEY_UP:
164 Ypos += step;
165 break;
166 case GLUT_KEY_DOWN:
167 Ypos -= step;
168 break;
169 case GLUT_KEY_LEFT:
170 Xpos -= step;
171 break;
172 case GLUT_KEY_RIGHT:
173 Xpos += step;
174 break;
175 }
176 glutPostRedisplay();
177 }
178
179
Init(GLboolean ciMode,const char * filename)180 static void Init( GLboolean ciMode, const char *filename )
181 {
182 printf("GL_VERSION = %s\n", (char *) glGetString(GL_VERSION));
183 printf("GL_RENDERER = %s\n", (char *) glGetString(GL_RENDERER));
184
185 Image = LoadRGBImage( filename, &ImgWidth, &ImgHeight, &ImgFormat );
186 if (!Image) {
187 printf("Couldn't read %s\n", filename);
188 exit(0);
189 }
190
191 if (ciMode) {
192 /* Convert RGB image to grayscale */
193 GLubyte *indexImage = (GLubyte *) malloc( ImgWidth * ImgHeight );
194 GLint i;
195 for (i=0; i<ImgWidth*ImgHeight; i++) {
196 int gray = Image[i*3] + Image[i*3+1] + Image[i*3+2];
197 indexImage[i] = gray / 3;
198 }
199 free(Image);
200 Image = indexImage;
201 ImgFormat = GL_COLOR_INDEX;
202
203 for (i=0;i<255;i++) {
204 float g = i / 255.0;
205 glutSetColor(i, g, g, g);
206 }
207 }
208
209 printf("Loaded %d by %d image\n", ImgWidth, ImgHeight );
210
211 glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
212 glPixelStorei(GL_UNPACK_ROW_LENGTH, ImgWidth);
213
214 Reset();
215 }
216
217
Usage(void)218 static void Usage(void)
219 {
220 printf("Keys:\n");
221 printf(" SPACE Reset Parameters\n");
222 printf(" Up/Down Move image up/down (SHIFT for large step)\n");
223 printf(" Left/Right Move image left/right (SHIFT for large step)\n");
224 printf(" x Decrease X-axis PixelZoom\n");
225 printf(" X Increase X-axis PixelZoom\n");
226 printf(" y Decrease Y-axis PixelZoom\n");
227 printf(" Y Increase Y-axis PixelZoom\n");
228 printf(" s Toggle GL_SCISSOR_TEST\n");
229 printf(" f Toggle front/back buffer drawing\n");
230 printf(" ESC Exit\n");
231 }
232
233
main(int argc,char * argv[])234 int main( int argc, char *argv[] )
235 {
236 GLboolean ciMode = GL_FALSE;
237 const char *filename = IMAGE_FILE;
238 int i = 1;
239
240 glutInitWindowSize( WinWidth, WinHeight );
241 glutInit( &argc, argv );
242
243 if (argc > i && strcmp(argv[i], "-ci")==0) {
244 ciMode = GL_TRUE;
245 i++;
246 }
247 if (argc > i) {
248 filename = argv[i];
249 }
250
251 if (ciMode)
252 glutInitDisplayMode( GLUT_INDEX | GLUT_DOUBLE );
253 else
254 glutInitDisplayMode( GLUT_RGB | GLUT_DOUBLE);
255
256 glutCreateWindow(argv[0]);
257 gladLoadGL();
258
259 Init(ciMode, filename);
260 Usage();
261
262 glutReshapeFunc( Reshape );
263 glutKeyboardFunc( Key );
264 glutSpecialFunc( SpecialKey );
265 glutDisplayFunc( Display );
266
267 glutMainLoop();
268 return 0;
269 }
270