TextureDrawer.cs

using Sandbox;
using System;

// ported from https://github.com/ProtoTurtle/UnityBitmapDrawing/blob/d73a977ad918ef1c6b3fa820432291dbed388e54/src/BitmapDrawing.cs

public class TextureDrawer
{

	private readonly Texture Texture;
	private readonly byte[] Data;
	private readonly int Width;
	private readonly int Height;

	public Vector2 Size => new( Width, Height );

	public TextureDrawer( Texture texture )
	{
		Texture = texture;
		Width = Texture.Width;
		Height = Texture.Height;

		var colors = texture.GetPixels();
		var pos = 0;

		Data = new byte[Width * Height * 4];

		foreach ( var color in colors )
		{
			Data[pos++] = color.r;
			Data[pos++] = color.g;
			Data[pos++] = color.b;
			Data[pos++] = color.a;
		}
	}

	public void Apply()
	{
		Texture.Update( Data );
	}

	public void DrawCircle( int x, int y, int radius, Color color, bool filled = false )
	{
		int cx = radius;
		int cy = 0;
		int radiusError = 1 - cx;

		while ( cx >= cy )
		{
			if ( !filled )
			{
				PlotCircle( cx, x, cy, y, color );
			}
			else
			{
				ScanLineCircle( cx, x, cy, y, color );
			}

			cy++;

			if ( radiusError < 0 )
			{
				radiusError += 2 * cy + 1;
			}
			else
			{
				cx--;
				radiusError += 2 * (cy - cx + 1);
			}
		}
	}

	public void DrawPixel( int x, int y, Color32 color )
	{
		if ( x < 0 || x > Texture.Width || y < 0 || y > Texture.Height )
		{
			return;
		}

		var idx = ToIndex( x, y );
		Data[idx] = color.r;
		Data[idx + 1] = color.g;
		Data[idx + 2] = color.b;
		Data[idx + 3] = color.a;
	}

	public void DrawPixels( int x, int y, int width, int height, Color32 color )
	{
		for ( int px = x; px < x + width; px++ )
		{
			for ( int py = y; py < y + height; py++ )
			{
				var idx = ToIndex( px, py );
				Data[idx++] = color.r;
				Data[idx++] = color.g;
				Data[idx++] = color.b;
				Data[idx++] = color.a;
			}
		}
	}

	public void DrawLine( int x0, int y0, int x1, int y1, Color color )
	{
		int width = Texture.Width;
		int height = Texture.Height;

		bool isSteep = Math.Abs( y1 - y0 ) > Math.Abs( x1 - x0 );
		if ( isSteep )
		{
			Swap( ref x0, ref y0 );
			Swap( ref x1, ref y1 );
		}
		if ( x0 > x1 )
		{
			Swap( ref x0, ref x1 );
			Swap( ref y0, ref y1 );
		}

		int deltax = x1 - x0;
		int deltay = Math.Abs( y1 - y0 );

		int error = deltax / 2;
		int ystep;
		int y = y0;

		if ( y0 < y1 )
			ystep = 1;
		else
			ystep = -1;

		for ( int x = x0; x < x1; x++ )
		{
			if ( isSteep )
				DrawPixel( y, x, width, height, color );
			else
				DrawPixel( x, y, width, height, color );

			error = error - deltay;
			if ( error < 0 )
			{
				y = y + ystep;
				error = error + deltax;
			}
		}
	}

	public void DrawRectangle( Rect rectangle, Color color )
	{
		int x = (int)rectangle.Position.x;
		int y = (int)rectangle.Position.y;
		int height = (int)rectangle.Height;
		int width = (int)rectangle.Width;

		DrawLine( x, y, x, y + height, color );
		DrawLine( x, y + height, x + width, y + height, color );
		DrawLine( x + width, y + height, x + width, y, color );
		DrawLine( x + width, y, x, y, color );
	}

	public void DrawFilledRectangle( Rect rectangle, Color color )
	{
		DrawPixels( (int)rectangle.Position.x, (int)rectangle.Position.y,
			(int)rectangle.Width, (int)rectangle.Height, color );
	}

	private void DrawPixel( int x, int y, int width, int height, Color32 color )
	{
		if ( x < 0 || x > width || y < 0 || y > height )
		{
			return;
		}

		DrawPixel( x, y, color );
	}

	private void PlotCircle( int cx, int x, int cy, int y, Color color )
	{
		DrawPixel( cx + x, cy + y, color ); // Point in octant 1...
		DrawPixel( cy + x, cx + y, color );
		DrawPixel( -cx + x, cy + y, color );
		DrawPixel( -cy + x, cx + y, color );
		DrawPixel( -cx + x, -cy + y, color );
		DrawPixel( -cy + x, -cx + y, color );
		DrawPixel( cx + x, -cy + y, color );
		DrawPixel( cy + x, -cx + y, color ); // ... point in octant 8
	}

	private void ScanLineCircle( int cx, int x, int cy, int y, Color color )
	{
		DrawLine( cx + x, cy + y, -cx + x, cy + y, color );
		DrawLine( cy + x, cx + y, -cy + x, cx + y, color );
		DrawLine( -cx + x, -cy + y, cx + x, -cy + y, color );
		DrawLine( -cy + x, -cx + y, cy + x, -cx + y, color );
	}

	private int ToIndex( int x, int y )
	{
		x = Math.Clamp( x, 0, Texture.Width - 1 );
		y = Math.Clamp( y, 0, Texture.Height - 1 );

		return ((y * Texture.Width) + x) * 4;
	}

	private void Swap( ref int x, ref int y )
	{
		int temp = x;
		x = y;
		y = temp;
	}

}




/**
The MIT License (MIT)
Copyright (c) 2014 Lauri Hosio
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.
 */