Skip to content

Instantly share code, notes, and snippets.

@atruskie
Last active January 12, 2022 08:27
Show Gist options
  • Save atruskie/02f6fb35d6967c57ed543d109e83736e to your computer and use it in GitHub Desktop.
Save atruskie/02f6fb35d6967c57ed543d109e83736e to your computer and use it in GitHub Desktop.
System.Drawing and SkiaSharp - fill blending via opacity channel for rgb (no alpha) image
using SixLabors.ImageSharp;
using SixLabors.ImageSharp.Drawing.Processing;
using SixLabors.ImageSharp.Processing;
using SkiaSharp;
using System;
using System.IO;
namespace ConsoleApp1
{
class Program
{
static void Main(string[] args)
{
ImageSharp();
CairoImage();
SkiaSharp();
SystemDrawing();
}
public static void ImageSharp()
{
Console.WriteLine("Hello World!");
var image = new SixLabors.ImageSharp.Image<SixLabors.ImageSharp.PixelFormats.Rgb24>(SixLabors.ImageSharp.Configuration.Default, 100, 100, SixLabors.ImageSharp.Color.Black);
image.Mutate(x => x.Fill(SixLabors.ImageSharp.Color.Red.WithAlpha(0.5f), new RectangleF(10, 10, 80, 80)));
image.Save("rgb24demo_imagesharp.png");
}
public static void CairoImage()
{
var surface = new Cairo.ImageSurface(Cairo.Format.Rgb24, 100, 100);
using (var cr = new Cairo.Context(surface))
{
cr.Color = new Cairo.Color(0, 0, 0);
cr.Fill();
cr.Color = new Cairo.Color(1, 0, 0, 0.5);
cr.Rectangle(10, 10, 80, 80);
cr.Fill();
}
surface.WriteToPng("rgb24demo_cairo.png");
}
public static void SkiaSharp()
{
using var image = new SKBitmap(new SKImageInfo(100, 100, SKColorType.Rgb888x));
using (var canvas = new SKCanvas(image))
{
canvas.Clear(SKColors.Black);
SKPaint redFill = new SKPaint
{
Style = SKPaintStyle.Fill,
Color = SKColors.Red.WithAlpha(128),
};
canvas.DrawRect(10, 10, 80, 80, redFill);
canvas.Flush();
}
using (var save = SKImage.FromBitmap(image))
using (var data = save.Encode(SKEncodedImageFormat.Png, 100))
{
// save the data to a stream
using (var stream = File.OpenWrite("rgb24demo_skia.png"))
{
data.SaveTo(stream);
}
}
}
public static void SystemDrawing()
{
using var sdImage = new System.Drawing.Bitmap(100, 100, System.Drawing.Imaging.PixelFormat.Format24bppRgb);
using (var graphics = System.Drawing.Graphics.FromImage(sdImage))
{
graphics.Clear(System.Drawing.Color.Black);
graphics.FillRectangle(new System.Drawing.SolidBrush(System.Drawing.Color.FromArgb(128, 255, 0, 0)), new System.Drawing.Rectangle(10, 10, 80, 80));
}
using (var stream = File.OpenWrite("rgb24demo_system.drawing.png"))
{
sdImage.Save(stream, System.Drawing.Imaging.ImageFormat.Png);
}
}
}
}
@atruskie
Copy link
Author

For future reference, this example was made for SixLabors/ImageSharp.Drawing#38

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment