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amoskoh
10-27-2004, 09:52 PM
I have a 2d orthogonal projection and im trying to texture map a bmp on the whole screen as a background. However when I run this code, nothing gets mapped, all white. The front portion of this code is something i got from Nehe that grabs info from the bmp into the byte array. I checked the byte array and it looks fine.



#include <stdio.h>
#include <stdlib.h>
#include <GL/gl.h>
#include <GL/glu.h>
#include <GL/glut.h>

#define WINDOW_WIDTH 430
#define WINDOW_HEIGHT 360


/* storage for one texture */
int texture[1];

/* Image type - contains height, width, and data */
struct Image {
unsigned long sizeX;
unsigned long sizeY;
char *data;
};
typedef struct Image Image;

// quick and dirty bitmap loader...for 24 bit bitmaps with 1 plane only.
// See http://www.dcs.ed.ac.uk/~mxr/gfx/2d/BMP.txt for more info.
int ImageLoad(char *filename, Image *image) {
FILE *file;
unsigned long size; // size of the image in bytes.
unsigned long i; // standard counter.
unsigned short int planes; // number of planes in image (must be 1)
unsigned short int bpp; // number of bits per pixel (must be 24)
char temp; // temporary color storage for bgr-rgb conversion.
float ff;
int ii;
int j, k;
char c;
// make sure the file is there.
if ((file = fopen(filename, "rb"))==NULL)
{
printf("File Not Found : %s\n",filename);
return 0;
}

// seek through the bmp header, up to the width/height:
fseek(file, 18, SEEK_CUR);

// read the width
if ((i = fread(&amp;image->sizeX, 4, 1, file)) != 1) {
printf("Error reading width from %s.\n", filename);
return 0;
}
printf("Width of %s: %lu\n", filename, image->sizeX);

// read the height
if ((i = fread(&amp;image->sizeY, 4, 1, file)) != 1) {
printf("Error reading height from %s.\n", filename);
return 0;
}
printf("Height of %s: %lu\n", filename, image->sizeY);

// calculate the size (assuming 24 bits or 3 bytes per pixel).
size = image->sizeX * image->sizeY * 3;

// read the planes
if ((fread(&amp;planes, 2, 1, file)) != 1) {
printf("Error reading planes from %s.\n", filename);
return 0;
}
if (planes != 1) {
printf("Planes from %s is not 1: %u\n", filename, planes);
return 0;
}


// read the bpp
if ((i = fread(&amp;bpp, 2, 1, file)) != 1) {
printf("Error reading bpp from %s.\n", filename);
return 0;
}
if (bpp != 24) {
printf("Bpp from %s is not 24: %u\n", filename, bpp);
return 0;
}

// seek past the rest of the bitmap header.
fseek(file, 24, SEEK_CUR);

// read the data.
image->data = (char *) malloc(size);
if (image->data == NULL) {
printf("Error allocating memory for color-corrected image data");
return 0;
}


if ((i = fread(image->data, size, 1, file)) != 1) {
printf("Error reading image data from %s.\n", filename);
return 0;
}
/


for (i=0;i<size;i+=3) { // reverse all of the colors. (bgr -> rgb)
temp = image->data[i];
image->data[i] = image->data[i+2];
image->data[i+2] = temp;
}
// we're done.
return 1;
}

// Load Bitmaps And Convert To Textures
void LoadGLTextures(char *filename) {
// Load Texture
Image *image1;

// allocate space for texture
image1 = (Image *) malloc(sizeof(Image));
if (image1 == NULL) {
printf("Error allocating space for image");
exit(0);
}

if (!ImageLoad(filename, image1)) {
exit(1);
}

// Create Texture
glGenTextures(1, &amp;texture[0]);
glBindTexture(GL_TEXTURE_2D, texture[0]); // 2d texture (x and y size)

glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTE R,GL_LINEAR); // scale linearly when image bigger than texture
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTE R,GL_LINEAR); // scale linearly when image smalled than texture

// 2d texture, level of detail 0 (normal), 3 components (red, green, blue), x size from image, y size from image,
// border 0 (normal), rgb color data, unsigned byte data, and finally the data itself.
glTexImage2D(GL_TEXTURE_2D, 0, 3, image1->sizeX, image1->sizeY, 0, GL_RGB, GL_UNSIGNED_BYTE, image1->data);
};


void myinit(char* filename)
{
LoadGLTextures(filename);
glEnable(GL_TEXTURE_2D);
glClearColor(1.0, 1.0, 1.0, 0.0);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluOrtho2D(0, WINDOW_WIDTH, 0, WINDOW_HEIGHT);

}

// Draw ground
void drawGround()
{
glBindTexture(GL_TEXTURE_2D, texture[0]); // choose the texture to use. glBegin(GL_POLYGON);

glTexCoord2f(0.0f, 0.0f); glVertex2i(0, 0); // Bottom Left Of The Texture and Quad
glTexCoord2f(0.0f, 1.0f); glVertex2i( 0, WINDOW_HEIGHT); // Top Left Of The Texture and Quad
glTexCoord2f(1.0f, 1.0f); glVertex2i( WINDOW_WIDTH, WINDOW_HEIGHT); // Top Right Of The Texture and Quad
glTexCoord2f(1.0f, 0.0f); glVertex2i( WINDOW_WIDTH, 0); // Bottom Right Of The Texture and Quad
glEnd();

glFlush();
}



// Display function
void display()
{
// Clear buffer
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
// Set up texture and draw ground
drawGround();
glutSwapBuffers();
}


int main (int argc, char ** argv)
{
/* Initialize glut */
glutInit(&amp;argc,argv);

/* Set up window modes */
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);

/* Set window position (where it will appear when it opens) */
glutInitWindowPosition(0,0);

/* Set size of window */
glutInitWindowSize(WINDOW_WIDTH, WINDOW_HEIGHT);

/* Create the window */
glutCreateWindow("War Simulator");

/* Turn on depth testing */
glEnable(GL_DEPTH_TEST);

/* tells glut to use a particular display function to redraw */
glutDisplayFunc(display);

/* Set idle function. You can change this to call code for your animation,
* or place your animation code in doIdle */
glutIdleFunc(doIdle);

/* do initialization */
myinit(argv[1]);

/* Begin GL loop */
glutMainLoop();

return 0;
}

amoskoh
10-27-2004, 10:05 PM
OK.. I think I know why it didnt work. My bmp picture was 430 X360 pixels. Is that why nothing showed up? So I need to add padding to make it 512X512?

amoskoh
10-27-2004, 10:11 PM
Unfortunately.. its still nothing even when I used a 512X512 bitmap

RigidBody
10-27-2004, 10:46 PM
you can use gluScaleImage to scale any image to 256x256 or 512x512 etc.

by the way, you don't have to rearrange the bitmap data if you use GL_BGR instead of GL_RGB in glTexImage2D.

concerning the textures- i usually use these settings:

GLuint tex;
char tex_data[];

glGenTextures(1, &tex);
glBindTexture(GL_TEXTURE_2D, tex);
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_LINEAR);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
glTexImage2D(GL_TEXTURE_2D, 0, 3, 256, 256, 0, GL_BGR, GL_UNSIGNED_BYTE, tex_data);

i see you defined your texture name as 'int textures[]'- it should be GLuint.

amoskoh
10-28-2004, 09:21 PM
Thats not the problem (defining it as texture[], im just using the first number in the array.
Anyone have any ideas? Im sure I did the steps right..

RigidBody
10-28-2004, 10:45 PM
well, look at this line from drawGround():

glBindTexture(GL_TEXTURE_2D, texture[0]); // choose the texture to use. glBegin(GL_POLYGON);

the two slashes make the rest of the line a comment. if you put glBegin(GL_POLYGON) in a new line, it should work.

amoskoh
10-29-2004, 07:18 AM
I love you GreetingsFromMunich. you are awesome!

RigidBody
10-29-2004, 08:53 AM
:) thank you very much. to avoid this in the future, a good idea would be to use an editor which can do syntax highlighting (like nedit, if you program in linux). these editors usually put c/c++ -keywords in different colors, maybe in a bold font, and comments are displayed in italic font. in nedit, your code would look something like

void drawGround() {
glBindTexture(GL_TEXTURE_2D, texture[0]); // choose the texture to use. glBegin(GL_POLYGON);

you can immediately see if there's a syntax error- if you type 'vodi' instead of 'void', it is not displayed in bold. and you see that glBegin(GL_POLYGON) is interpreted as a comment.