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khaled1990khaled
10-10-2015, 07:44 PM
Hi,


I just want to know how to save an image in opengl code ?

I know that in opencv, I have to type imwrite("image.jbg, functionName );

But how about the opengl ?

Thanks

hidefromkgb
10-10-2015, 11:47 PM
Unlike OpenCV, OpenGL does not contain immediate picture loading or saving routines, so you have to implement them yourself when you need them. The details on how to achieve this will largely depend on the source and destination of the image.

khaled1990khaled
10-11-2015, 12:15 AM
Can I post my code and you help me how can I save the image ?

Thanks

hidefromkgb
10-11-2015, 12:52 PM
Ok, why not. Just remember to use the
tag.

khaled1990khaled
10-11-2015, 02:24 PM
#include "stdafx.h"
#include <stdlib.h>
#include <gl/glut.h>

// 4 control points for our cubic bezier curve
float Points[4][3] = {
{ 10,10,0 },
{ 5,10,2 },
{ -5,0,0 },
{-10,5,-2}
};

// the level of detail of the curve
unsigned int LOD=20;


void OnKeyPress(unsigned char key,int,int) {
switch(key) {

// increase the LOD
case '+':
++LOD;
break;

// decrease the LOD
case '-':
--LOD;

// have a minimum LOD value
if (LOD<3)
LOD=3;
break;
default:
break;
}

// ask glut to redraw the screen for us...
glutPostRedisplay();
}

void OnDraw() {

// clear the screen & depth buffer
glClear(GL_DEPTH_BUFFER_BIT|GL_COLOR_BUFFER_BIT);

// clear the previous transform
glLoadIdentity();

// set the camera position
gluLookAt( 1,10,30, // eye pos
0,0,0, // aim point
0,1,0); // up direction

glColor3f(1,0,1);

// we will draw lots of little lines to make our curve
glBegin(GL_LINE_STRIP);

for(int i=0;i!=LOD;++i) {

// use the parametric time value 0 to 1
float t = (float)i/(LOD-1);

// nice to pre-calculate 1.0f-t because we will need it frequently
float it = 1.0f-t;

// calculate blending functions
float b0 = t*t*t;
float b1 = 3*t*t*it;
float b2 = 3*t*it*it;
float b3 = it*it*it;

// calculate the x,y and z of the curve point by summing
// the Control vertices weighted by their respective blending
// functions
//
float x = b0*Points[0][0] +
b1*Points[1][0] +
b2*Points[2][0] +
b3*Points[3][0] ;

float y = b0*Points[0][1] +
b1*Points[1][1] +
b2*Points[2][1] +
b3*Points[3][1] ;

float z = b0*Points[0][2] +
b1*Points[1][2] +
b2*Points[2][2] +
b3*Points[3][2] ;

// specify the point
glVertex3f( x,y,z );
}
glEnd();

// draw the Control Vertices
glColor3f(0,1,0);
glPointSize(3);
glBegin(GL_POINTS);
for(int i=0;i!=4;++i) {
glVertex3fv( Points[i] );
}
glEnd();

// draw the hull of the curve
glColor3f(0,1,1);
glBegin(GL_LINE_STRIP);
for(int i=0;i!=4;++i) {
glVertex3fv( Points[i] );
}
glEnd();

// currently we've been drawing to the back buffer, we need
// to swap the back buffer with the front one to make the image visible
glutSwapBuffers();
}


void OnInit() {
// enable depth testing
glEnable(GL_DEPTH_TEST);
}


void OnExit() {
}


void OnReshape(int w, int h)
{
if (h==0)
h=1;

// set the drawable region of the window
glViewport(0,0,w,h);

// set up the projection matrix
glMatrixMode(GL_PROJECTION);
glLoadIdentity();

// just use a perspective projection
gluPerspective(45,(float)w/h,0.1,100);

// go back to modelview matrix so we can move the objects about
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
}


int main(int argc,char** argv) {

// initialise glut
glutInit(&argc,argv);

// request a depth buffer, RGBA display mode, and we want double buffering
glutInitDisplayMode(GLUT_DEPTH|GLUT_RGBA|GLUT_DOUB LE);

// set the initial window size
glutInitWindowSize(640,480);

// create the window
glutCreateWindow("Bezier Curve: +/- to Change Level of Detail");

// set the function to use to draw our scene
glutDisplayFunc(OnDraw);

// set the function to handle changes in screen size
glutReshapeFunc(OnReshape);

// set the function for the key presses
glutKeyboardFunc(OnKeyPress);

// run our custom initialisation
OnInit();

// set the function to be called when we exit
atexit(OnExit);

// this function runs a while loop to keep the program running.
glutMainLoop();
return 0;
}

__bob__
10-12-2015, 06:22 AM
Hi, here his my code to save openGL image as PPM (size 1024*1024 in my case; just add with and heigt)



void PPMWriter(unsigned char *in,char *name,int dimx, int dimy)
{

int i, j;
FILE *fp = fopen(name, "wb"); /* b - binary mode */
(void) fprintf(fp, "P6\n%d %d\n255\n", dimx, dimy);
for (j = 0; j < dimy; ++j)
{
for (i = 0; i < dimx; ++i)
{
static unsigned char color[3];
color[0] = in[3*i+3*j*dimy]; /* red */
color[1] = in[3*i+3*j*dimy+1]; /* green */
color[2] = in[3*i+3*j*dimy+2]; /* blue */
(void) fwrite(color, 1, 3, fp);
}
}
(void) fclose(fp);
}

void saveImage( float Ttime, int nbr)
{
unsigned char* image = (unsigned char*)malloc(sizeof(unsigned char) * 3 * 1024 * 1024);
glReadPixels(0, 0, 1024, 1024, GL_RGB, GL_UNSIGNED_BYTE, image);
// Warning : enregistre de bas en haut
char buffer [33];
sprintf(buffer,"capture/%d SV-%f ms.ppm",nbr,Ttime) ;


PPMWriter(image,buffer,1024, 1024);
}