如何加载纹理Opengl？(How to load texture Opengl?)
我在这个站点找到了一个有用的帖子，其中一些代码用于加载BMP这段代码应该加载标题，读出信息，更进一步，读取数据，生成纹理并将其装箱。 但它不起作用。 我究竟做错了什么 ？
纹理声明：
GLuint texture[1];BMP装载：
void LoadTexture(char *filename) { FILE * file = fopen(filename,"rb"); unsigned char header[54]; unsigned int dataPos; unsigned int imageSize; unsigned int width, height; fread(header,1,54,file); dataPos = *(int*)&(header[0x0A]); imageSize = *(int*)&(header[0x22]); width = *(int*)&(header[0x12]); height = *(int*)&(header[0x16]); if (imageSize==0) { imageSize=width*height*3; } if (dataPos==0) { dataPos=54; } unsigned char data[imageSize]; fseek(file, SEEK_SET, 53); fread(data,1,imageSize,file); fclose(file); glActiveTexture(GL_TEXTURE1); glGenTextures(1, texture[0]); glBindTexture(GL_TEXTURE_2D, texture[0]); glTexImage2D(GL_TEXTURE_2D, 0,GL_RGB, width, height, 0, GL_BGR, GL_UNSIGNED_BYTE, data); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR); glGenerateMipmap(GL_TEXTURE_2D); glBindTexture(GL_TEXTURE_2D, texture[0]); }编辑 ：我打印出从标题中读取的一些值。 标题似乎正确读取。
画画 ：
int DrawGLScene(GLvoid) { glLoadIdentity(); glEnable(GL_TEXTURE_2D); glTranslatef(0.0f,0.0f,-5.0f); glActiveTexture(GL_TEXTURE1); glBindTexture(GL_TEXTURE_2D, texture[0]); glBegin(GL_QUADS); glTexCoord2f(0.0f, 0.0f); glVertex3f(-1.0f, -1.0f, 1.0f); glTexCoord2f(1.0f, 0.0f); glVertex3f( 1.0f, -1.0f, 1.0f); glTexCoord2f(1.0f, 1.0f); glVertex3f( 1.0f, 1.0f, 1.0f); glTexCoord2f(0.0f, 1.0f); glVertex3f(-1.0f, 1.0f, 1.0f); glTexCoord2f(1.0f, 0.0f); glVertex3f(-1.0f, -1.0f, -1.0f); glTexCoord2f(1.0f, 1.0f); glVertex3f(-1.0f, 1.0f, -1.0f); glTexCoord2f(0.0f, 1.0f); glVertex3f( 1.0f, 1.0f, -1.0f); glTexCoord2f(0.0f, 0.0f); glVertex3f( 1.0f, -1.0f, -1.0f); glTexCoord2f(0.0f, 1.0f); glVertex3f(-1.0f, 1.0f, -1.0f); glTexCoord2f(0.0f, 0.0f); glVertex3f(-1.0f, 1.0f, 1.0f); glTexCoord2f(1.0f, 0.0f); glVertex3f( 1.0f, 1.0f, 1.0f); glTexCoord2f(1.0f, 1.0f); glVertex3f( 1.0f, 1.0f, -1.0f); glTexCoord2f(1.0f, 1.0f); glVertex3f(-1.0f, -1.0f, -1.0f); glTexCoord2f(0.0f, 1.0f); glVertex3f( 1.0f, -1.0f, -1.0f); glTexCoord2f(0.0f, 0.0f); glVertex3f( 1.0f, -1.0f, 1.0f); glTexCoord2f(1.0f, 0.0f); glVertex3f(-1.0f, -1.0f, 1.0f); glTexCoord2f(1.0f, 0.0f); glVertex3f( 1.0f, -1.0f, -1.0f); glTexCoord2f(1.0f, 1.0f); glVertex3f( 1.0f, 1.0f, -1.0f); glTexCoord2f(0.0f, 1.0f); glVertex3f( 1.0f, 1.0f, 1.0f); glTexCoord2f(0.0f, 0.0f); glVertex3f( 1.0f, -1.0f, 1.0f); glTexCoord2f(0.0f, 0.0f); glVertex3f(-1.0f, -1.0f, -1.0f); glTexCoord2f(1.0f, 0.0f); glVertex3f(-1.0f, -1.0f, 1.0f); glTexCoord2f(1.0f, 1.0f); glVertex3f(-1.0f, 1.0f, 1.0f); glTexCoord2f(0.0f, 1.0f); glVertex3f(-1.0f, 1.0f, -1.0f); glEnd(); glFlush(); glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); return 1; }I found a useful post at this site, where some code is used to load a BMP This code should load the header, read out infos, go further, read data, generate texture and bin it. But it doesnt work. What am I doing wrong ?
Texture Declaration :
GLuint texture[1];BMP Loading :
void LoadTexture(char *filename) { FILE * file = fopen(filename,"rb"); unsigned char header[54]; unsigned int dataPos; unsigned int imageSize; unsigned int width, height; fread(header,1,54,file); dataPos = *(int*)&(header[0x0A]); imageSize = *(int*)&(header[0x22]); width = *(int*)&(header[0x12]); height = *(int*)&(header[0x16]); if (imageSize==0) { imageSize=width*height*3; } if (dataPos==0) { dataPos=54; } unsigned char data[imageSize]; fseek(file, SEEK_SET, 53); fread(data,1,imageSize,file); fclose(file); glActiveTexture(GL_TEXTURE1); glGenTextures(1, texture[0]); glBindTexture(GL_TEXTURE_2D, texture[0]); glTexImage2D(GL_TEXTURE_2D, 0,GL_RGB, width, height, 0, GL_BGR, GL_UNSIGNED_BYTE, data); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR); glGenerateMipmap(GL_TEXTURE_2D); glBindTexture(GL_TEXTURE_2D, texture[0]); }EDIT : I printed out some values read from the header. The header seems to be read properly.
Drawing :
int DrawGLScene(GLvoid) { glLoadIdentity(); glEnable(GL_TEXTURE_2D); glTranslatef(0.0f,0.0f,-5.0f); glActiveTexture(GL_TEXTURE1); glBindTexture(GL_TEXTURE_2D, texture[0]); glBegin(GL_QUADS); glTexCoord2f(0.0f, 0.0f); glVertex3f(-1.0f, -1.0f, 1.0f); glTexCoord2f(1.0f, 0.0f); glVertex3f( 1.0f, -1.0f, 1.0f); glTexCoord2f(1.0f, 1.0f); glVertex3f( 1.0f, 1.0f, 1.0f); glTexCoord2f(0.0f, 1.0f); glVertex3f(-1.0f, 1.0f, 1.0f); glTexCoord2f(1.0f, 0.0f); glVertex3f(-1.0f, -1.0f, -1.0f); glTexCoord2f(1.0f, 1.0f); glVertex3f(-1.0f, 1.0f, -1.0f); glTexCoord2f(0.0f, 1.0f); glVertex3f( 1.0f, 1.0f, -1.0f); glTexCoord2f(0.0f, 0.0f); glVertex3f( 1.0f, -1.0f, -1.0f); glTexCoord2f(0.0f, 1.0f); glVertex3f(-1.0f, 1.0f, -1.0f); glTexCoord2f(0.0f, 0.0f); glVertex3f(-1.0f, 1.0f, 1.0f); glTexCoord2f(1.0f, 0.0f); glVertex3f( 1.0f, 1.0f, 1.0f); glTexCoord2f(1.0f, 1.0f); glVertex3f( 1.0f, 1.0f, -1.0f); glTexCoord2f(1.0f, 1.0f); glVertex3f(-1.0f, -1.0f, -1.0f); glTexCoord2f(0.0f, 1.0f); glVertex3f( 1.0f, -1.0f, -1.0f); glTexCoord2f(0.0f, 0.0f); glVertex3f( 1.0f, -1.0f, 1.0f); glTexCoord2f(1.0f, 0.0f); glVertex3f(-1.0f, -1.0f, 1.0f); glTexCoord2f(1.0f, 0.0f); glVertex3f( 1.0f, -1.0f, -1.0f); glTexCoord2f(1.0f, 1.0f); glVertex3f( 1.0f, 1.0f, -1.0f); glTexCoord2f(0.0f, 1.0f); glVertex3f( 1.0f, 1.0f, 1.0f); glTexCoord2f(0.0f, 0.0f); glVertex3f( 1.0f, -1.0f, 1.0f); glTexCoord2f(0.0f, 0.0f); glVertex3f(-1.0f, -1.0f, -1.0f); glTexCoord2f(1.0f, 0.0f); glVertex3f(-1.0f, -1.0f, 1.0f); glTexCoord2f(1.0f, 1.0f); glVertex3f(-1.0f, 1.0f, 1.0f); glTexCoord2f(0.0f, 1.0f); glVertex3f(-1.0f, 1.0f, -1.0f); glEnd(); glFlush(); glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); return 1; }最满意答案
查看您如何阅读数据。 读取BMP后可以设置dataPos ， size等。 它是在图像文件的标题中定义的相对位置。
然后查看glTexImage2D（）。 您正在传递data而不是dataPos 。
Finally, after browsing the internet quite a lot, I found this working example :
#include <stdlib.h> #include <string.h> #include <GL/glut.h> #include <GL/gl.h> #include <GL/glu.h> #include <stdio.h> #include <math.h> GLuint texture[2]; struct Image { unsigned long sizeX; unsigned long sizeY; char *data; }; typedef struct Image Image; #define checkImageWidth 64 #define checkImageHeight 64 GLubyte checkImage[checkImageWidth][checkImageHeight][3]; void makeCheckImage(void){ int i, j, c; for (i = 0; i < checkImageWidth; i++) { for (j = 0; j < checkImageHeight; j++) { c = ((((i&0x8)==0)^((j&0x8)==0)))*255; checkImage[i][j][0] = (GLubyte) c; checkImage[i][j][1] = (GLubyte) c; checkImage[i][j][2] = (GLubyte) c; } } } 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. // 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(&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(&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(&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 bitsperpixel if ((i = fread(&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; } Image * loadTexture(){ Image *image1; // allocate space for texture image1 = (Image *) malloc(sizeof(Image)); if (image1 == NULL) { printf("Error allocating space for image"); exit(0); } if (!ImageLoad("NeHe.bmp", image1)) { exit(1); } return image1; } void myinit(void) { glClearColor (0.5, 0.5, 0.5, 0.0); glEnable(GL_DEPTH_TEST); glDepthFunc(GL_LESS); Image *image1 = loadTexture(); if(image1 == NULL){ printf("Image was not returned from loadTexture\n"); exit(0); } makeCheckImage(); glPixelStorei(GL_UNPACK_ALIGNMENT, 1); // Create Texture glGenTextures(2, texture); glBindTexture(GL_TEXTURE_2D, texture[0]); glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR); //scale linearly when image bigger than texture glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR); //scale linearly when image smalled than texture glTexImage2D(GL_TEXTURE_2D, 0, 3, image1->sizeX, image1->sizeY, 0, GL_RGB, GL_UNSIGNED_BYTE, image1->data); glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_DECAL); glBindTexture(GL_TEXTURE_2D, texture[1]); glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP); glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP); glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_DECAL); glTexImage2D(GL_TEXTURE_2D, 0, 3, checkImageWidth, checkImageHeight, 0, GL_RGB, GL_UNSIGNED_BYTE,&checkImage[0][0][0]); glEnable(GL_TEXTURE_2D); glShadeModel(GL_FLAT); } void display(void){ glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glBindTexture(GL_TEXTURE_2D, texture[1]); glutSolidTeapot(1.0); glBindTexture(GL_TEXTURE_2D, texture[0]); glBegin(GL_QUADS); glTexCoord2f(0.0, 0.0); glVertex3f(1.0, -1.0, 0.0); glTexCoord2f(1.0, 0.0); glVertex3f(1.0, 1.0, 0.0); glTexCoord2f(1.0, 1.0); glVertex3f(2.41421, 1.0, -1.41421); glTexCoord2f(0.0, 1.0); glVertex3f(2.41421, -1.0, -1.41421); glEnd(); glutSwapBuffers(); } void myReshape(int w, int h){ glViewport(0, 0, w, h); glMatrixMode(GL_PROJECTION); glLoadIdentity(); gluPerspective(60.0, 1.0*(GLfloat)w/(GLfloat)h, 1.0, 30.0); glMatrixMode(GL_MODELVIEW); glLoadIdentity(); glTranslatef(0.0, 0.0, -3.6); } void keyboard (unsigned char key, int x, int y){ switch (key) { case 27: // “esc” on keyboard exit(0); break; default: // “a” on keyboard break; } } int main(int argc, char** argv) { glutInit(&argc, argv); glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH); glutCreateWindow("Texture Mapping - Programming Techniques"); myinit(); glutReshapeFunc (myReshape); glutDisplayFunc(display); glutKeyboardFunc(keyboard); glutMainLoop(); return 0; }更多推荐
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