ogmg/utils.cpp

#include "utils.h"

unsigned char * DecodeBMP(unsigned char * bmpFileData, int & width, int & height)
{
	if (0x4D42 == *((unsigned short*)bmpFileData)) {//通过前两个字节去判断数据是否是BMP数据
		int pixelDataOffset = *((int*)(bmpFileData + 10));//取出位图像素数据的偏移地址、
		width = *((int*)(bmpFileData + 18));//获取图片宽度
		height = *((int*)(bmpFileData + 22));//获取图片宽度

		/*读取图片内容*/
		unsigned char* pixelData = bmpFileData + pixelDataOffset;
		for (int i = 0; i < width * height * 3; i += 3) {
			unsigned char temp = pixelData[i];
			//BGR 转换成 RGB
			pixelData[i] = pixelData[i + 2];
			pixelData[i + 2] = temp;
		}
		return pixelData;
	}
	return nullptr;
}

GLuint CreateTexture2D(unsigned char * pixelData, int width, int height, GLenum type)
{
	GLuint texture;
	glGenTextures(1, &texture);

	//绑定纹理
	glBindTexture(GL_TEXTURE_2D, texture);

	//设置纹理放大/缩小时候数据采集的算法
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);//使用线性过滤
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);//使用线性过滤

	//设置当纹理坐标大于1.0时候的数据采集方式
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP);

	//数据上传到显卡
	glTexImage2D(GL_TEXTURE_2D, 0, type, width, height, 0, type, GL_UNSIGNED_BYTE, pixelData);

	//释放纹理
	glBindTexture(GL_TEXTURE_2D, 0);
	return texture;
}

GLuint CreateTexture2DFromBMP(const char * bmpPath)
{
	int nFileSize = 0;
	unsigned char* bmpFileContent = LoadFileContent(bmpPath, nFileSize);

	if (bmpFileContent == nullptr) {
		return 0;
	}

	int bmpWidth = 0;
	int bmpHeight = 0;
	unsigned char* pixelData = DecodeBMP(bmpFileContent, bmpWidth, bmpHeight);

	if (bmpWidth == 0) {
		delete bmpFileContent;
		return 0;
	}

	GLuint textrue = CreateTexture2D(pixelData, bmpWidth, bmpHeight, GL_RGB);

	return textrue;
}

GLuint CreateDisplayList(std::function<void()> foo)
{
	GLuint displayList = glGenLists(1);//申请一个显示列表

	glNewList(displayList, GL_COMPILE);
	foo();
	glEndList();

	return displayList;
}