Graphics32

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Basic Drawing & Shapes ​

Welcome to Graphics32! If you are used to working with standard Delphi or Lazarus TBitmap or GDI canvases, drawing in Graphics32 (TBitmap32) will feel familiar yet significantly more flexible and powerful.

TBitmap32 provides direct 32-bit pixel storage where each pixel contains Red, Green, Blue, and Alpha channels. In this tutorial, you will learn how to create a bitmap, clear its surface, draw fundamental geometric shapes, and control pen colors.

1. Creating and Setting Up TBitmap32 ​

Before drawing anything, you need an instance of TBitmap32. Unlike standard GDI bitmaps, TBitmap32 lives entirely in 32-bit memory, making pixel operations fast and consistent across platforms.

pascal
uses
  Classes, SysUtils, GR32;

var
  Bitmap: TBitmap32;
begin
  // Create an instance of TBitmap32
  Bitmap := TBitmap32.Create;
  try
    // Set width and height (Width = 600, Height = 400)
    // The third parameter, Clear = False, instructs SetSize not to
    // clear the bitmap.
    Bitmap.SetSize(600, 400, False);

    // Clear the background to solid white ($FFFFFFFF)
    Bitmap.Clear(clWhite32);

    // Your drawing operations go here...

    // Save the result to disk
    Bitmap.SaveToFile('drawing_output.png');
  finally
    Bitmap.Free;
  end;
end;

INFO

The reason why we are not clearing the bitmap when setting the size (Bitmap.SetSize(Width, Height, False)) is that on the very next line we do clear the bitmap to the desired color (clWhite32 in this case). If we also cleared the bitmap in SetSize it would just be a waste of time.

Key Takeaways ​

  • SetSize(Width, Height): Allocates memory for specified width and height.
  • Clear(Color): Fills the entire surface with a single TColor32 value in one fast memory operation.
  • Memory Management: Always wrap your bitmap allocation inside a try...finally block to prevent memory leaks.

2. Drawing Lines and Framed Shapes ​

TBitmap32 maintains an internal pen state for simple 2D line drawing (PenColor, PenPos). You can position the virtual pen using MoveTo and draw connected line segments using LineTo or LineToAS (anti-aliased).

pascal
// Configure pen appearance
Bitmap.PenColor := clBlack32; // Solid black ($FF000000)

// Draw an anti-aliased triangle
Bitmap.MoveTo(100, 300);
Bitmap.LineToAS(300, 100);
Bitmap.LineToAS(500, 300);
Bitmap.LineToAS(100, 300);

// Draw an unfilled (framed) rectangle
// FrameRectS takes integer coordinates (Left, Top, Right, Bottom)
Bitmap.FrameRectS(50, 50, 550, 350, clGray32);

Understanding Anti-Aliasing (LineToAS) ​

Graphics32 offers both standard integer-binned line routines and anti-aliased line routines ending with AS (e.g. LineToAS). Anti-aliasing blends edge pixels with the background color to produce smooth, non-jagged lines.

3. Filled Rectangles ​

Filling areas with color is a common task in graphics applications. TBitmap32 includes optimized routines for solid rectangle fills.

pascal
// 1. Solid filled rectangle
// FillRectS(Left, Top, Right, Bottom, Color)
Bitmap.FillRectS(60, 60, 200, 180, clRed32);

// 2. Translucent filled rectangle
// FillRectTS blends the fill color with underlying pixels
Bitmap.FillRectTS(120, 100, 300, 240, clTrBlue32);

Method Naming Convention Quick-Reference ​

  • *S suffix (e.g., FillRectS, FrameRectS): Performs automatic boundary checking (clipping) against bitmap boundaries, preventing out-of-bounds crashes.
  • *TS suffix (e.g., FillRectTS): Performs boundary checking and alpha blending with existing pixels.

See also: Naming Conventions

Summary ​

In this example, you learned how to:

  1. Instaniate a TBitmap32 and set its canvas dimensions.
  2. Clear the surface to a solid background color.
  3. Use MoveTo and LineToAS to draw smooth anti-aliased lines.
  4. Fill rectangular regions with solid or semi-transparent colors using FillRectS and FillRectTS.

Next, proceed to the Alpha Blending & Transparency tutorial to learn how 32-bit color channels and alpha composition modes work in Graphics32!