如何在 C++ 中将位图绘制为 OpenGL 纹理？

Question

我有一个位图及其句柄（Win32 HBITMAP）。关于如何在 OpenGL 四边形上绘制此位图（缩放并​​拉动位图的 4 个角以适合四边形的 4 个顶点）有什么建议吗？

Answer 1

您需要检索 HBITMAP 中包含的数据，请参阅 http://msdn.microsoft.com/en-us/library/dd144879(v=vs.85).aspx 然后您可以使用以下命令将 DIB 数据上传到 OpenGL glTexImage2D 或 glTexSubImage2D

创建纹理后，您可以像往常一样应用它（启用纹理，为四边形的每个角指定一个纹理坐标）。

由于评论而编辑

这段（未经测试！）代码应该可以解决问题

GLuint load_bitmap_to_texture(
    HDC device_context, 
    HBITMAP bitmap_handle, 
    bool flip_image) /* untested */
{
    const int BytesPerPixel = sizeof(DWORD);

    SIZE bitmap_size;
    if( !GetBitmapDimensionEx(bitmap_handle, &bitmap_size) )
        return 0;

    ssize_t bitmap_buffer_size = bitmap_size.cx * bitmap_size.cy * BytesPerPixel;

#ifdef USE_DWORD
    DWORD *bitmap_buffer;
#else
    void *bitmap_buffer;
#endif
    bitmap_buffer = malloc(bitmap_buffer_size);

    if( !bitmap_buffer )
        return 0;


    BITMAPINFO bitmap_info;
    memset(&bitmap_info, 0, sizeof(bitmap_info));
    bitmap_info.bmiHeader.biSize = sizeof(bitmap_info.bmiHeader);
    bitmap_info.bmiHeader.biWidth  = bitmap_size.cx;
    bitmap_info.bmiHeader.biHeight = bitmap_size.cy;
    bitmap_info.bmiHeader.biPlanes = 1;
    bitmap_info.bmiHeader.biBitCount = BitsPerPixel;
    bitmap_info.bmiHeader.biCompression = BI_RGB;

    if( flip_image ) /* this tells Windows where to set the origin (top or bottom) */
        bitmap_info.bmiHeader.biHeight *= -1;

    if( !GetDIBits(device_context, 
                   bitmap_handle, 
                   0, bitmap_size.cy, 
                   bitmap_buffer, 
                   &bitmap_info,
                   DIB_RGB_COLORS /* irrelevant, but GetDIBits expects a valid value */ )
     ) {
        free(bitmap_buffer);
        return 0;
    }

    GLuint texture_name;
    glGenTextures(1, &texture_name);
    glBindTexture(GL_TEXTURE_2D, texture_name);

    glPixelStorei(GL_UNPACK_SWAP_BYTES, GL_FALSE);
    glPixelStorei(GL_UNPACK_LSB_FIRST,  GL_TRUE);
    glPixelStorei(GL_UNPACK_ROW_LENGTH, 0);
    glPixelStorei(GL_UNPACK_SKIP_PIXELS, 0);
    glPixelStorei(GL_UNPACK_SKIP_ROWS, 0);
    glPixelStorei(GL_UNPACK_ALIGNMENT, 1);

    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA,
                 bitmap_size.cx, bitmap_size.cy, 0,
                 GL_RGBA,
#ifdef USE_DWORD
                 GL_UNSIGNED_INT_8_8_8_8,
#else
                 GL_UNSIGNED_BYTE, 
#endif
                 bitmap_buffer);

    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); 
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

    free(bitmap_buffer);

    return texture_name;
}