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93 lines
3.5 KiB
C#
93 lines
3.5 KiB
C#
#region License Information (GPL v3)
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/*
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ShareX - A program that allows you to take screenshots and share any file type
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Copyright (c) 2007-2024 ShareX Team
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This program is free software; you can redistribute it and/or
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modify it under the terms of the GNU General Public License
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as published by the Free Software Foundation; either version 2
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of the License, or (at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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Optionally you can also view the license at <http://www.gnu.org/licenses/>.
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*/
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#endregion License Information (GPL v3)
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using System;
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using System.Collections;
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using System.Drawing;
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namespace ShareX.HelpersLib
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{
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/// <summary>
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/// Summary description for PaletteQuantizer.
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/// </summary>
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public class GrayscaleQuantizer : PaletteQuantizer
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{
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/// <summary>
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/// Construct the palette quantizer
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/// </summary>
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/// <remarks>
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/// Palette quantization only requires a single quantization step
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/// </remarks>
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public GrayscaleQuantizer()
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: base(new ArrayList())
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{
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_colors = new Color[256];
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int nColors = 256;
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// Initialize a new color table with entries that are determined
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// by some optimal palette-finding algorithm; for demonstration
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// purposes, use a grayscale.
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for (uint i = 0; i < nColors; i++)
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{
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uint Alpha = 0xFF; // Colors are opaque.
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uint Intensity = Convert.ToUInt32(i * 0xFF / (nColors - 1)); // Even distribution.
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// The GIF encoder makes the first entry in the palette
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// that has a ZERO alpha the transparent color in the GIF.
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// Pick the first one arbitrarily, for demonstration purposes.
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// Create a gray scale for demonstration purposes.
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// Otherwise, use your favorite color reduction algorithm
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// and an optimum palette for that algorithm generated here.
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// For example, a color histogram, or a median cut palette.
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_colors[i] = Color.FromArgb((int)Alpha,
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(int)Intensity,
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(int)Intensity,
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(int)Intensity);
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}
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}
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/// <summary>
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/// Override this to process the pixel in the second pass of the algorithm
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/// </summary>
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/// <param name="pixel">The pixel to quantize</param>
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/// <returns>The quantized value</returns>
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protected override byte QuantizePixel(Color32 pixel)
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{
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double luminance = (pixel.Red * 0.299) + (pixel.Green * 0.587) + (pixel.Blue * 0.114);
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// Gray scale is an intensity map from black to white.
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// Compute the index to the grayscale entry that
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// approximates the luminance, and then round the index.
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// Also, constrain the index choices by the number of
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// colors to do, and then set that pixel's index to the
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// byte value.
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byte colorIndex = (byte)(luminance + 0.5);
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return colorIndex;
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}
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}
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} |