www.pudn.com > flightsim.rar > texture.c

/* 
 * Texture image routines from Chapter 8. 
 * 
 * Written by Michael Sweet 
 */ 
 
/* 
 * Include necessary headers. 
 */ 
 
#include "texture.h" 
 
 
/* 
 * 'TextureLoad()' - Load a bitmap file and define it as a 1D or 2D texture. 
 * 
 * Returns 0 on success or -1 on error. 
 */ 
 
GLuint                           /* O - Texture object or 0 on error */ 
TextureLoad(char      *filename, /* I - Bitmap file to load */ 
            GLboolean alpha,     /* I - Generate alpha for bitmap */ 
            GLenum    minfilter, /* I - Minification filter */ 
	    GLenum    magfilter, /* I - Magnification filter */ 
	    GLenum    wrap)      /* I - Repeat or clamp */ 
    { 
    int         i;               /* Looping var */ 
    BITMAPINFO	*info;           /* Bitmap information */ 
    GLubyte	*bits;           /* Bitmap RGB pixels */ 
    GLubyte     *ptr;            /* Pointer into bit buffer */ 
    GLubyte     temp;            /* Swapping variable */ 
    GLenum      type;            /* Texture type */ 
    GLuint      texture;         /* Texture object */ 
 
    /* Try loading the bitmap file... */ 
    bits = LoadDIBitmap(filename, &info); 
    if (bits == (GLubyte *)0) 
        return (0); 
 
#ifdef WIN32 /* This already done by non-WIN32 LoadDIBitmap */ 
    /* 
     * Convert the bitmap data from BGR to RGB. Since texture images 
     * must be a power of two, and since we can figure that we won't 
     * have a texture image as small as 2x2 pixels, we ignore any 
     * alignment concerns... 
     */ 
 
    for (i = info->bmiHeader.biWidth * info->bmiHeader.biHeight, ptr = bits; 
         i > 0; 
	 i --, ptr += 3) 
        { 
	/* Swap red and blue */ 
	temp   = ptr[0]; 
	ptr[0] = ptr[2]; 
	ptr[2] = temp; 
	} 
#endif /* WIN32 */ 
 
    /* Figure out the type of texture... */ 
    if (info->bmiHeader.biHeight == 1) 
        type = GL_TEXTURE_1D; 
    else 
        type = GL_TEXTURE_2D; 
 
    /* Create and bind a texture object */ 
    glGenTextures(1, &texture); 
    glBindTexture(type, texture); 
 
    /* Set texture parameters */ 
    glTexParameteri(type, GL_TEXTURE_MAG_FILTER, magfilter); 
    glTexParameteri(type, GL_TEXTURE_MIN_FILTER, minfilter); 
    glTexParameteri(type, GL_TEXTURE_WRAP_S, wrap); 
    glTexParameteri(type, GL_TEXTURE_WRAP_T, wrap); 
    glTexEnvi(type, GL_TEXTURE_ENV_MODE, GL_MODULATE); 
 
    /* 
     * Set texture image; if the minification filter uses mip-mapping 
     * then use gluBuild2D/1DMipmaps() to load the texture... 
     */ 
 
    if (minfilter == GL_LINEAR || minfilter == GL_NEAREST) 
        glTexImage2D(type, 0, 3, info->bmiHeader.biWidth, 
                     info->bmiHeader.biHeight, 0, GL_RGB, 
                     GL_UNSIGNED_BYTE, bits); 
    else if (type == GL_TEXTURE_1D) 
        gluBuild1DMipmaps(type, 3, info->bmiHeader.biWidth, 
                          GL_RGB, GL_UNSIGNED_BYTE, bits); 
    else 
        gluBuild2DMipmaps(type, 3, info->bmiHeader.biWidth, 
                          info->bmiHeader.biHeight, GL_RGB, 
                          GL_UNSIGNED_BYTE, bits); 
 
    /* Free the bitmap and return... */ 
    free(info); 
    free(bits); 
 
    return (texture); 
    }