Windows Graphics Device Interface (GDI)

The Graphics Device Interface (GDI) is a core component of the Microsoft Windows operating system responsible for presenting graphical information to users. GDI provides a set of functions that applications can use to draw lines, curves, text, and graphics primitives on various output devices such as displays, printers, and plotters.

This section of the MSDN Community provides a comprehensive reference to the GDI API, covering its functions, structures, data types, and concepts. Whether you are developing graphical applications, drivers, or system-level components, understanding GDI is crucial for effective graphics programming on Windows.

Key GDI Concepts

• Device Context (DC): A structure that contains information about a particular device and the graphics attributes that apply to it. All GDI drawing operations are performed through a device context.
• GDI Objects: Resources that can be selected into a device context to control drawing attributes. These include pens, brushes, fonts, bitmaps, and regions.
• Coordinate Systems: Understanding world, page, and device coordinates is essential for accurate drawing.
• Bitmaps and Metafiles: Techniques for storing and manipulating graphical images.

Core GDI Function Categories

Example Usage (Conceptual)

Here's a simplified conceptual example of how you might use GDI to draw a red line:

HDC hdc = GetDC(NULL); // Get a device context for the screen

if (hdc != NULL) {
    // Create a red pen
    HPEN hPen = CreatePen(PS_SOLID, 2, RGB(255, 0, 0));
    if (hPen != NULL) {
        // Select the pen into the device context
        HPEN hOldPen = (HPEN)SelectObject(hdc, hPen);

        // Draw a line from (10, 10) to (100, 100)
        MoveToEx(hdc, 10, 10, NULL);
        LineTo(hdc, 100, 100);

        // Restore the original pen
        SelectObject(hdc, hOldPen);

        // Clean up the pen
        DeleteObject(hPen);
    }

    // Release the device context
    ReleaseDC(NULL, hdc);
}