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Canvas Class

Package: GHIElectronics.Endpoint.Drawing
Namespace: GHIElectronics.Endpoint.Drawing

A pixel buffer plus the primitives to draw into it. Pick the size and PixelFormat at Create time; when done, hand Buffer to whichever device accepts bytes: DisplayController.Flush, SpiDevice.Write, I2cDevice.Write, a file, anywhere.

public sealed class Canvas : IDisposable

Example​

using var canvas = Canvas.Create(240, 320, PixelFormat.Rgb565);
canvas.Clear(Color.Black);
canvas.DrawLine(10, 10, 230, 310, Color.Red, thickness: 2);
canvas.FillCircle(120, 160, 40, Color.Blue);
canvas.DrawText("Hello Endpoint", font, 10, 30, 20, Color.White);
spi.Write(canvas.Buffer);

Properties​

Buffer​

public byte[] Buffer { get; }

Raw pixel bytes. Length and layout match Width, Height, and PixelFormat. Hand this to any device that accepts a byte buffer.

Returns byte[]

Height​

public int Height { get; }

Height in pixels.

Returns int

PixelFormat​

public PixelFormat PixelFormat { get; }

Pixel layout of Buffer.

Returns PixelFormat

Width​

public int Width { get; }

Width in pixels.

Returns int

Methods​

Create(int width, int height, PixelFormat format)​

public static Canvas Create(int width, int height, PixelFormat format)

Allocate a new Canvas of the given size and pixel format. Dispose it when done to release the buffer promptly.

ParameterTypeDescription
widthintWidth in pixels.
heightintHeight in pixels.
formatPixelFormatPixel layout of the new buffer.

Returns Canvas

Clear(Color color)​

public void Clear(Color color)

Fill the whole buffer with a single color.

SetPixel(int x, int y, Color color)​

public void SetPixel(int x, int y, Color color)

Set a single pixel. No-op if (x, y) is outside the canvas.

DrawLine(int x0, int y0, int x1, int y1, Color color, int thickness)​

public void DrawLine(int x0, int y0, int x1, int y1, Color color, int thickness = 1)

Bresenham line, honoring thickness by stamping an r-pixel disc at each step.

DrawRectangle(int x, int y, int width, int height, Color color, int thickness)​

public void DrawRectangle(int x, int y, int width, int height, Color color, int thickness = 1)

Stroke a rectangle outline.

FillRectangle(int x, int y, int width, int height, Color color)​

public void FillRectangle(int x, int y, int width, int height, Color color)

Fill a rectangle.

DrawCircle(int cx, int cy, int radius, Color color, int thickness)​

public void DrawCircle(int cx, int cy, int radius, Color color, int thickness = 1)

Midpoint-algorithm circle outline.

FillCircle(int cx, int cy, int radius, Color color)​

public void FillCircle(int cx, int cy, int radius, Color color)

Filled circle.

DrawText(string text, Font font, int x, int y, int sizePx, Color color)​

public void DrawText(string text, Font font, int x, int y, int sizePx, Color color)

Rasterize text with font at sizePx, with the top-left of the text box at (x, y). Alpha-blends against whatever is already in the canvas. The font is rasterized on every call; cache into a Canvas and re-blit if you need high FPS. Rgb565 and Monochrome targets only.

DrawImage(Image image, int x, int y)​

public void DrawImage(Image image, int x, int y)

Blit a pre-decoded Image into this canvas at (x, y). The image's internal pixels are converted to this canvas's PixelFormat on the fly. Prefer this over the raw-bytes overload in redraw loops: decoding a JPG is ~150 ms; blitting a cached Image is a few ms.

DrawImage(byte[] fileBytes, int x, int y)​

public void DrawImage(byte[] fileBytes, int x, int y)

Decode an image file (JPEG / PNG / BMP / GIF / TGA, detected from the file's magic bytes) and blit it into this canvas at (x, y). Clips to the canvas bounds. Convenience one-shot. For repeated draws, cache the decode via Image.Load and call the Image overload.

DrawImage(byte[] pixels, int x, int y, int width, int height, PixelFormat format)​

public void DrawImage(byte[] pixels, int x, int y, int width, int height, PixelFormat format)

Blit a decoded pixel buffer into this canvas at (x, y). Pixels outside the canvas bounds are clipped.

Dispose()​

public void Dispose()

Release the pixel buffer.