OpenGL-保存BMP图片

Posted 2020-07-13

bool screenshot(const char* filename)
{
GLenum lastBuffer;
GLbyte* pBits = 0; // 图像数据
unsigned long lImageSize;
GLint iViewport[4]; // 视图大小

glGetIntegerv(GL_VIEWPORT, iViewport);
lImageSize = iViewport[2] * iViewport[3] * 3;

pBits = (GLbyte*)new unsigned char[lImageSize];
if (!pBits)
return false;

// 从color buffer中读取数据
glPixelStorei(GL_PACK_ALIGNMENT, 1);
glPixelStorei(GL_PACK_ROW_LENGTH, 0);
glPixelStorei(GL_PACK_SKIP_ROWS, 0);
glPixelStorei(GL_PACK_SKIP_PIXELS, 0);

//
glGetIntegerv(GL_READ_BUFFER, (GLint*)&lastBuffer);
glReadBuffer(GL_FRONT);
glReadPixels(0, 0, iViewport[2], iViewport[3], GL_BGR_EXT, GL_UNSIGNED_BYTE, pBits);
glReadBuffer(lastBuffer);

if (writeBMP(filename, (unsigned char*)pBits, iViewport[2], iViewport[3]))
return true;

return false;

}


bool writeBMP(const char filename[], unsigned char* data, unsigned int w, unsigned int h)
{
std::ofstream out_file;

/** 检查data */
if(!data) 
{
std::cerr << "data corrupted! " << std::endl;
out_file.close();
return false;
}

/** 创建位图文件信息和位图文件头结构 */
BITMAPFILEHEADER header;
BITMAPINFOHEADER bitmapInfoHeader;

//unsigned char textureColors = 0;/**< 用于将图像颜色从BGR变换到RGB */

/** 打开文件,并检查错误 */
out_file.open(filename, std::ios::out | std::ios::binary);
if (!out_file)
{
std::cerr << "Unable to open file " << filename << std::endl;
return false;
}

/** 填充BITMAPFILEHEADER */
header.bfType = BITMAP_ID;
header.bfSize = w*h*3 + sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER);
header.bfReserved1 = 0;
header.bfReserved2 = 0;
header.bfOffBits = sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER);
/** 写入位图文件头信息 */
out_file.write((char*)&header, sizeof(BITMAPFILEHEADER));

/** 填充BITMAPINFOHEADER */
bitmapInfoHeader.biSize = sizeof(BITMAPINFOHEADER);
bitmapInfoHeader.biWidth = w;
bitmapInfoHeader.biHeight = h;
bitmapInfoHeader.biPlanes = 1;
bitmapInfoHeader.biBitCount = 24;
bitmapInfoHeader.biCompression = BI_RGB; // BI_RLE4 BI_RLE8
bitmapInfoHeader.biSizeImage = w * h * 3; // 当压缩类型为BI_RGB是也可以设置为0
bitmapInfoHeader.biXPelsPerMeter = 0;
bitmapInfoHeader.biYPelsPerMeter = 0;
bitmapInfoHeader.biClrUsed = 0;
bitmapInfoHeader.biClrImportant = 0;
/** 写入位图文件信息 */
out_file.write((char*)&bitmapInfoHeader, sizeof(BITMAPINFOHEADER));

/** 将指针移到数据开始位置 */
out_file.seekp(header.bfOffBits, std::ios::beg);

/** 写入图像数据 */
out_file.write((char*)data, bitmapInfoHeader.biSizeImage);

out_file.close();
return true;
}