Canvasity

canvasity DUB package is a port of the C++ library canvas_ity.h as seen here. It provides a canvas type Canvasity similar to HTML Canvas API.

Features

• Familiar Canvas API
• CSS color Support through the colors DUB package.
• Lines, quadratic and bezier paths.
• Line joins, line caps.
• fill() AND stroke().
• Support shadowBlur.
• Support setLineDash.
• Support lineWidth.
• Support save/restore properly.
• Support clip paths.
• Support globalAlpha and most globalCompositeOperation modes.
• Trapezoidal anti-aliasing.
• Gamma-aware rect blending, interpolation, and resampling.
• Premultiplied blending.
• Support various underlying buffer types, 1 to 4 channels:
  • sRGB 8-bit
  • sRGB 16-bit
  • sRGB 32-bit float
• Quality options with CanvasOptions.
• Suitable for -betterC, nothrow @nogc.
• Amortized allocations, all buffers are reused.
• SIMD optimizations. But for more performance for filled paths, consider using dplug:canvas.
• Stringly typed constants, but also enums for performance.

Future

• Restore support for gradients
• Restore and solidify support for fonts
• Restore dither
• Restore image pattern fill
• Display-P3 support

Limitations

The library does no input or output on its own. Instead, you must provide it with buffers to copy into or out of. This buffer must be a gamut Image.

Examples

1. Drawing rectangles

import canvasity;
import gamut;

void main() {

    Image image;
    image.create(250, 250, PixelType.rgba8);

    Canvasity canvas = Canvasity(image);
    canvas.fillStyle = "#fff";
    canvas.fillRect(0, 0, 250, 250);
    canvas.fillStyle("red");
    canvas.fillRect(140, 20, 40, 250);
    canvas.fillStyle("blue");
    canvas.fillRect(50, 50, 150, 100);

    image.saveToFile("output-rectangle.png");
}

2. Applying Strokes with .stroke()

This example illustrate how .fill() and .stroke may be used in any order.

import canvasity;
import gamut;

void main() {

    Image image;
    image.create(300, 150, PixelType.rgba16);

    with(Canvasity(image)) {

        lineWidth = 30;
        strokeStyle = "red";
        lineJoin = "round";

        // Stroke on top of fill
        beginPath;
        rect(25, 25, 100, 100);
        fill;
        stroke;

        // Fill on top of stroke
        beginPath;
        rect(175, 25, 100, 100);
        stroke;
        fill;
    }
    image.convertTo8Bit();
    image.saveToFile("output-shadow.png");
}

3. Adding a shadow to a shape

This example adds a blurred shadow to a rectangle. The shadowColor property sets its color, and shadowBlur sets its level of blurriness.

import canvasity;
import gamut;

void main() {

    Image image;
    image.create(300, 300, PixelType.rgba16);

    with(Canvasity(image)) {
        shadowBlur    = 20;
        shadowOffsetX = 10;
        shadowOffsetY = 10;
        shadowColor("rgba(0, 0, 0, 0.5)");
        fillStyle("purple");
        fillRect(60, 60, 190, 190);
    }

    image.saveToFile("output-shadow.png");
}