OpenGL_ES加载TGA/BMP纹理

清疚 2022-08-05 02:13 241阅读 0赞

typedef struct TGAImage											{
    	GLubyte	*imageData;											// 	图像数据
    	GLuint	bpp;												// 	像素颜色深度
    	GLuint	width;												//      图像宽度
    	GLuint	height;												// 	图像高度
    	GLuint	texID;																	//	纹理ID
    } TGAImage;	
    bool LoadTGA(TGAImage *texture, char *filename)
    {
    	GLubyte		TGAheader[12]={0,0,2,0,0,0,0,0,0,0,0,0};		// Uncompressed TGA Header			不压缩的TGA头
    	GLubyte		TGAcompare[12];									// Used To Compare TGA Header		压缩的
    	GLubyte		header[6];										// First 6 Useful Bytes From The Header		TGA头的前6个有用的字节
    	GLuint		bytesPerPixel;									// Holds Number Of Bytes Per Pixel Used In The TGA File		TGA文件每个像素使用的字节
    	GLuint		imageSize;										// Used To Store The Image Size When Setting Aside Ram
    	GLuint		temp;											// Temporary Variable		临时变量
    	GLuint		type=GL_RGBA;									// Set The Default GL Mode To RBGA (32 BPP)	默认的GL模式
    	FILE *file = fopen(filename, "rb");							// Open The TGA File
    	printf("TGA_file=%d/n",file);
    	if(	file==NULL ||											// Does File Even Exist?
    		fread(TGAcompare,1,sizeof(TGAcompare),file)!=sizeof(TGAcompare) ||	// Are There 12 Bytes To Read?		是否读到12字节数据
    		memcmp(TGAheader,TGAcompare,sizeof(TGAheader))!=0				||	// Does The Header Match What We Want?	是否是压缩的，压缩的就读取失败，关闭file
    		fread(header,1,sizeof(header),file)!=sizeof(header))				// If So Read Next 6 Header Bytes		再读6个字节
    	{
    		if (file == NULL)										// Did The File Even Exist? *Added Jim Strong*
    			return false;										// Return False
    		else													// Otherwise
    		{
    			fclose(file);										// If Anything Failed, Close The File
    			return false;										// Return False
    		}
    	}
    	
    	//12到17字节前四字节是图像宽高，第五字节是图像位深度
    	texture->width  = header[1] * 256 + header[0];				// Determine The TGA Width	(highbyte*256+lowbyte)//低字节，高字节
    	texture->height = header[3] * 256 + header[2];				// Determine The TGA Height	(highbyte*256+lowbyte)
    	if(	texture->width	<=0	||									// Is The Width Less Than Or Equal To Zero
    		texture->height	<=0	||									// Is The Height Less Than Or Equal To Zero
    		(header[4]!=24 && header[4]!=32))						// Is The TGA 24 or 32 Bit?		
    	{
    		fclose(file);											// If Anything Failed, Close The File
    		return false;											// Return False
    	}
    	texture->bpp	= header[4];								// Grab The TGA's Bits Per Pixel (24 or 32)
    	bytesPerPixel	= texture->bpp/8;							// Divide By 8 To Get The Bytes Per Pixel	每个像素使用的字节数
    	imageSize		= texture->width*texture->height*bytesPerPixel;	// Calculate The Memory Required For The TGA Data
    	texture->imageData=(GLubyte *)malloc(imageSize);			// Reserve Memory To Hold The TGA Data	申请内存
    	if(	texture->imageData==NULL ||								// Does The Storage Memory Exist?
    		fread(texture->imageData, 1, imageSize, file)!=imageSize)	// Does The Image Size Match The Memory Reserved?	图像数据保存到纹理结构数据缓存imageData中
    	{//失败情况下释放资源
    		if(texture->imageData!=NULL)							// Was Image Data Loaded
    			free(texture->imageData);							// If So, Release The Image Data
    		fclose(file);											// Close The File
    		return false;											// Return False
    	}
    	for(GLuint i=0; i<int(imageSize); i+=bytesPerPixel)			// Loop Through The Image Data
    	{															// Swaps The 1st And 3rd Bytes ('R'ed and 'B'lue)
    		temp=texture->imageData[i];								// Temporarily Store The Value At Image Data 'i'
    		texture->imageData[i] = texture->imageData[i + 2];		// Set The 1st Byte To The Value Of The 3rd Byte
    		texture->imageData[i + 2] = temp;						// Set The 3rd Byte To The Value In 'temp' (1st Byte Value)
    	}
    	fclose (file);												// Close The File
    	glGenTextures(1, &texture->texID);							// Generate生产，产生 OpenGL texture IDs
    	printf("纹理ID=%d/n",texture->texID );
    	glBindTexture(GL_TEXTURE_2D, texture->texID);						// Bind 绑定Our Texture
    	glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);	// Linear Filtered
    	glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);	// Linear Filtered
    	glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
    	glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
    	if (texture[0].bpp==24)										// Was The TGA 24 Bits
    	{
    		type=GL_RGB;											// If So Set The 'type' To GL_RGB
    	}
    	//创建纹理
    	glTexImage2D(GL_TEXTURE_2D, 0, type, texture->width, texture->height, 0, type, GL_UNSIGNED_BYTE, texture->imageData);
    	return true;
    }
    bool LoadBMP(TGAImage *texture, char *filename)
    {
    	
    	BITMAPFILEHEADER	bmpFileHeader;		//bmp文件头 
    	BITMAPINFOHEADER	bmpInfoHeader;			 //bmp格式头   
    	GLuint		imageSize;										//纹理数据大小
    	GLuint		temp;											// 		临时变量
    	GLuint		type=GL_RGB;									
    	FILE *file = fopen(filename, "rb");						
    	printf("BMP_file=%d/n",file);	
    	if(	file==NULL)											// Does File Even Exist?
    		return	false;
    	fread(&bmpFileHeader,1,sizeof(BITMAPFILEHEADER),file);	//读取文件头 
    	if(bmpFileHeader.bfType!=0x4d42)						//判断是否是BM 
    		return	false;
    	else
    		printf("是bmp图像/n");
    	
    	fread(&bmpInfoHeader,1,sizeof(BITMAPINFOHEADER),file);		//	读取信息头
    	texture->width	=	bmpInfoHeader.biWidth;				//图片宽度
    	texture->height	=	bmpInfoHeader.biHeight;				//图片高度
    	texture->bpp	=	bmpInfoHeader.biBitCount;			//位深度
    	imageSize		=	bmpInfoHeader.biSizeImage ;			//图像数据的大小，用作申请纹理缓存
    	if(	texture->width	<=0	||									
    		texture->height	<=0	||									
    		texture->bpp!=24)									// bmp不是24位图	
    	{
    		fclose(file);										
    		return false;										
    	}
    	//BITMAPFILEHEADER.bfOffBits从文件头开始到颜色数据的偏移量
    	fseek(file,bmpFileHeader.bfOffBits,SEEK_SET);	//移动指针到图像数据
    	texture->imageData=(GLubyte *)malloc(imageSize);
    	if(	texture->imageData==NULL ||								// Does The Storage Memory Exist?
    		fread(texture->imageData, 1, imageSize, file)!=imageSize)	// Does The Image Size Match The Memory Reserved?	图像数据保存到纹理结构数据缓存imageData中
    	{
    		//失败情况下释放资源
    		if(texture->imageData!=NULL)							// Was Image Data Loaded
    			free(texture->imageData);							// If So, Release The Image Data
    		fclose(file);											// Close The File
    		return false;											// Return False
    	}
    	for(GLuint i=0; i<int(imageSize); i+=texture->bpp/8)		// Loop Through The Image Data
    	{															// Swaps The 1st And 3rd Bytes ('R'ed and 'B'lue)
    		temp=texture->imageData[i];								// Temporarily Store The Value At Image Data 'i'
    		texture->imageData[i] = texture->imageData[i + 2];		// Set The 1st Byte To The Value Of The 3rd Byte
    		texture->imageData[i + 2] = temp;						// Set The 3rd Byte To The Value In 'temp' (1st Byte Value)
    	}
    	fclose (file);												// Close The File
    	glGenTextures(1, &texture->texID);							// Generate生产，产生 OpenGL texture IDs
    	printf("纹理ID=%d/n",texture->texID );
    	glBindTexture(GL_TEXTURE_2D, texture->texID);						// Bind 绑定Our Texture
    	glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);	// Linear Filtered
    	glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);	// Linear Filtered
    	glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
    	glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
    	//创建纹理
    	glTexImage2D(GL_TEXTURE_2D, 0, type, texture->width, texture->height, 0, type, GL_UNSIGNED_BYTE, texture->imageData);
    	return true;
    }
    使用：
    	/*LoadTGA(&MainImage,"//NAND//skyworth//tga//main.tga/0");
    	LoadTGA(&MovieImage,"//NAND//skyworth//tga//movie.tga");*/
    	LoadBMP(&MainImage,"//USER//tv.bmp/0");
    	LoadBMP(&MovieImage,"//USER//music.bmp/0");

本文转自：http://blog.csdn.net/ezhong0812/article/details/6401723