Bitmap operations and OpenGL texture combination

//Texture Mapping Functionsvoid CCY457OpenGLView::LoadGLTextures(){    //Create Texture Names    glGenTextures(3, m_Texture);    LoadTexture("Apple.bmp",0);    LoadTexture("Fauve.bmp",1);    LoadTexture("Flower.bmp",2);}void CCY457OpenGLView::LoadTexture (CString fileName, int texName){    //Load Texture    AUX_RGBImageRec* m_texture;    m_texture = auxDIBImageLoad((const char*)fileName);    if(!m_texture)    {       MessageBox("Picture could not be loaded");       exit(1);    }    glBindTexture(GL_TEXTURE_2D, m_Texture[texName]);    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, m_texWrap);    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, m_texWrap);    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, m_texFilter);    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, m_texFilter);    glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, m_texMode);    gluBuild2DMipmaps(GL_TEXTURE_2D, 3, m_texture->sizeX,m_texture->sizeY, GL_RGB, GL_UNSIGNED_BYTE, m_texture->data);}

 

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Two days ago, we encountered a problem when using bitmap for texture. when 8-Bit Bitmap cannot be used, I came up with an idea and hoped to complete it. so I checked some file structures about bitmap. I will not detail the bitmap structure here. because there are already a lot of online reading methods and many people have implemented many reading methods. refer to this blog post: bitmap Overview

Actually. I didn't know that I already had a powerful open-source tool .. freeimage .. is an image file that supports all current formats .. so I basically wrote it in white. for details about 1 4 16 32, refer to its source code to complete the following classes:

Now I only wrote the source code for one afternoon: the details are not summarized, all of which indicate the comments in the class:

// ================================================ ==================================================//*** @ File BMP loader. h ** file Description: loaded bitmap * Applicable platform: Windows98/2000/NT/XP ** by: acmiyou * Email: acmiyou@qq.com * // ================================================= ==========================================================#include <windows. h> # include <stdio. h> # ifndef _ BMP loader_h _ # DEFINE _ BMP loader_h _ # define bitmap_id 0x4d42/** <symbol of the bitmap file */# define blue 0 # define Green 1 # def INE Red 2 # define swapcolor (a, B) {\ (a) ^ = (B); \ (B) ^ = (a); \ () ^ = (B); \} class BMP loader {public: BMP loader ();~ BMP loader (); void free ();/** release memory */bitmapinfoheader * bitinfo;/** record Bitmap header information */byte * image; /** image data */bool loadbitmap (const char * filename);/** load bitmap file */PRIVATE: void computepalettesize (); /** calculate the number of color table items in the bitmap */INT getimageline (INT width, int bitcount);/** calculate the number of bytes in each line, the result is a multiple of 4 */byte * getscanline (byte * data, int pitch, int scanline ); /** get the starting address of each row of pixel data */bool covertto24bits (byte * data);/** forcibly convert all types to 24-bit */void covertline8bto24b (byte * DST, byte * SRC);/** convert 8-bit behavior to 24-bit rows */rgbquad * p_colortable;/** color table */}; # endif

 

// ================================================ ==================================================//*** @ File BMP loader. CPP ** file Description: loaded bitmap * Applicable platform: Windows98/2000/NT/XP ** Author: acmiyou * Email: acmiyou@qq.com * // ================================================= ============================================================#include "BMP Loader. H "BMP Loader: BMP loader () {bitinfo = 0; image = 0; p_colortable = 0;} BMP Loader ::~ BMP loader () {free ();}/***** release occupied memory */void BMP Loader: Free () {If (image! = NULL) {Delete [] image; image = 0;} If (bitinfo! = NULL) {Delete [] bitinfo; bitinfo = 0;} If (p_colortable! = NULL) {Delete [] p_colortable; p_colortable = 0 ;}/ *** load a bitmap file ** @ Param: ** filename file name */bool BMP Loader :: loadbitmap (const char * filename) {/** if data already exists, release the memory */free ();/** release the memory */file * fp = fopen (filename, "rb"); If (FP = NULL) return false;/** file opening failed */bitmapfileheader header; fread (& header, sizeof (bitmapfileheader), 1, FP);/** read the bitmap file header */If (header. bftype! = Bitmap_id)/** returns */{free (); fclose (FP); Return false;} bitinfo = (bitmapinfoheader *) if it is not a bitmap type *) new byte [sizeof (bitmapinfoheader)]; fread (bitinfo, sizeof (bitmapinfoheader), 1, FP);/** bitmap information header */If (bitinfo-> bisize! = 40) {free (); Return false;/** this class is not compressed in RGB format but does not support reading failure */} computepalettesize (); /** calculate the color table value */If (bitinfo-> biclrused! = 0) {p_colortable = (rgbquad *) New byte [sizeof (rgbquad) * bitinfo-> biclrused]; fread (p_colortable, sizeof (rgbquad) * bitinfo-> biclrused, 1, FP);}/** bitmap pixel data size */bitinfo-> bisizeimage = getimageline (bitinfo-> biwidth, bitinfo-> bibitcount) * bitinfo-> biheight; byte * imagedata = new byte [bitinfo-> bisizeimage]; fseek (FP, header. bfoffbits, seek_set);/** read pixel information */fread (imagedata, bitinfo-> bisizeimage, 1, FP); fclose (F P);/** forced conversion to 24-bit */If (! Covertto24bits (imagedata)/** returns */{free (); Return false;} Delete [] imagedata if the format of 1 4 16 32 bits is not supported; /** convert BGR --> RGB */For (INT duration = 0; duration <bitinfo-> bisizeimage; duration ++ = 3) swapcolor (image [duration], image [watermark + 2]); Return true;}/*** calculate the number of color table items in the bitmap ** @ Param: none */void BMP Loader: computepalettesize () {/** only 1 4 8 has a color table */If (bitinfo-> biclrused = 0) {Switch (bitinfo-> bibitcount) {Case 1: bitinfo-> biclrused = 2; break; c ASE 4: bitinfo-> biclrused = 16; break; case 8: bitinfo-> biclrused = 256; break; Case 16: Case 24: Case 32: bitinfo-> biclrused = 0; break; default: Break ;}}/ *** calculate the number of bytes per line ** @ Param: ** width ** bitcount the number of bits per pixel ** @ return: number of row bytes */int bmp Loader: getimageline (INT width, int bitcount) {return (width * bitcount) + 7)/8 + 3 &~ 3;}/** get the starting address of each row of pixel data ** @ Param: ** data pixel data ** pitch pixel row bytes ** scanline line ** @ return: line start address */byte * BMP Loader: getscanline (byte * data, int pitch, int scanline) {return data + pitch * scanline;}/*** forcibly convert all types to 24-bit ** @ Param: ** data pixel data */bool BMP Loader: covertto24bits (byte * Data) {If (bitinfo = NULL | DATA = NULL) return false; int lineimage = getimageline (bitinfo-> biwidth, 24); int linedata = getimageline (bitinfo-> biwidth, bitinfo-> bibitcount ); bitinfo-> bisizeimage = lineimage * bitinfo-> biheight; image = new byte [bitinfo-> bisizeimage]; memset (image, 0, bitinfo-> bisizeimage ); switch (bitinfo-> bibitcount) {Case 1: Return false; Case 4: Return false; case 8: For (int row = 0; row <bitinfo-> biheight; row ++) covertline8bto24b (getscanline (image, lineimage, row), getscanline (data, linedata, row); break; Case 16: Return false; Case 24: memcpy (image, data, bitinfo-> bisizeimage); break; Case 32: Return false;} return true;}/*** convert 8-bit behavior 24-bit rows ** @ Param: ** DST Destination Address ** SRC Source Address */void BMP Loader: covertline8bto24b (byte * DST, byte * SRC) {for (INT Col = 0; Col <bitinfo-> biwidth; col ++) {/** convert the index value to the color in the color table */DST [Blue] = p_colortable [SRC [col]. rgbblue; DST [Green] = p_colortable [SRC [col]. rgbgreen; DST [Red] = p_colortable [SRC [col]. rgbred; DST + = 3 ;}}