【转】[PPTX解析] 图片 重新着色存储详解

using System;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Drawing.Imaging;

namespace ImageProcessService
{
    /// <summary>
    ///     颜色转换矩阵
    /// </summary>
    public static class ColorMatrices
    {
        /// <summary>
        /// 使用给定的数量创建亮度过滤器矩阵。
        /// <para>
        /// 使用算法<see href="https://cs.chromium.org/chromium/src/cc/paint/render_surface_filters.cc"/>
        /// </para>
        /// </summary>
        /// <remarks>
        /// 值为 0 将创建一个完全黑色的图像。值为 1 时输入保持不变。
        /// 其他值是效果的线性乘数。允许超过 1 的值，从而提供更明亮的结果。
        /// </remarks>
        /// <param name="amount">转化比例，必须大于或等于 0。</param>
        /// <returns>The <see cref="ColorMatrix"/>.</returns>
        public static ColorMatrix CreateBrightnessMatrix(float amount)
        {
            if (amount < 0)
            {
                throw new ArgumentOutOfRangeException(nameof(amount), "Threshold must be >= 0");
            }

            return new ColorMatrix
            {
                Matrix00 = amount,
                Matrix11 = amount,
                Matrix22 = amount,
                Matrix33 = 1F
            };
        }

        /// <summary>
        /// 使用给定的数量创建灰度滤波器矩阵。
        /// <para>
        /// 使用算法<see href="https://en.wikipedia.org/wiki/Luma_%28video%29#Rec._601_luma_versus_Rec._709_luma_coefficients"/>
        /// </para>
        /// </summary>
        /// <param name="amount">转化比例，必须大于或等于 0。</param>
        /// <returns>The <see cref="ColorMatrix"/>.</returns>
        public static ColorMatrix CreateGrayScaleMatrix(float amount)
        {
            if (amount < 0 || amount > 1)
            {
                throw new ArgumentOutOfRangeException(
                    nameof(amount),
                    "Threshold must be in range 0..1");
            }

            amount = 1F - amount;

            var matrix = new ColorMatrix();
            matrix.Matrix00 = .299F + (.701F * amount);
            matrix.Matrix10 = .587F - (.587F * amount);
            matrix.Matrix20 = 1F - (matrix.Matrix00 + matrix.Matrix10);

            matrix.Matrix01 = .299F - (.299F * amount);
            matrix.Matrix11 = .587F + (.2848F * amount);
            matrix.Matrix21 = 1F - (matrix.Matrix01 + matrix.Matrix11);

            matrix.Matrix02 = .299F - (.299F * amount);
            matrix.Matrix12 = .587F - (.587F * amount);
            matrix.Matrix22 = 1F - (matrix.Matrix02 + matrix.Matrix12);
            matrix.Matrix33 = 1F;

            return matrix;
        }

        /// <summary>
        /// 使用给定的数量创建对比度过滤器矩阵。
        /// <para>
        /// 使用算法<see href="https://cs.chromium.org/chromium/src/cc/paint/render_surface_filters.cc"/>
        /// </para>
        /// </summary>
        /// <remarks>
        /// 值为 0 将创建一个完全灰色的图像。值为 1 时输入保持不变。
        /// 其他值是效果的线性乘数。允许超过 1 的值，从而提供具有更高对比度的结果。
        /// </remarks>
        /// <param name="amount">转化比例，必须大于或等于 0。</param>
        /// <returns>The <see cref="ColorMatrix"/>.</returns>
        public static ColorMatrix CreateContrastMatrix(float amount)
        {
            if (amount < 0)
            {
                throw new ArgumentOutOfRangeException(nameof(amount), "Threshold must be >= 0");
            }

            var contrast = (-.5F * amount) + .5F;

            return new ColorMatrix
            {
                Matrix00 = amount,
                Matrix11 = amount,
                Matrix22 = amount,
                Matrix33 = 1F,
                Matrix40 = contrast,
                Matrix41 = contrast,
                Matrix42 = contrast
            };
        }

        /// <summary>
        /// 使用给定的数量创建饱和度过滤器矩阵。
        /// <para>
        /// 使用算法<see href="https://cs.chromium.org/chromium/src/cc/paint/render_surface_filters.cc"/>
        /// </para>
        /// </summary>
        /// <remarks>
        /// 0 值是完全不饱和的。值为 1 时输入保持不变。
        /// 其他值是效果的线性乘数。允许超过 1 的值，提供超饱和结果。
        /// </remarks>
        /// <param name="amount">转化比例，必须大于或等于 0。</param>
        /// <returns>The <see cref="ColorMatrix"/>.</returns>
        public static ColorMatrix CreateSaturationMatrix(float amount)
        {
            if (amount < 0)
            {
                throw new ArgumentOutOfRangeException(nameof(amount), "Threshold must be >= 0");
            }

            var matrix = new ColorMatrix();
            matrix.Matrix00 = .213F + (.787F * amount);
            matrix.Matrix10 = .715F - (.715F * amount);
            matrix.Matrix20 = 1F - (matrix.Matrix00 + matrix.Matrix10);

            matrix.Matrix01 = .213F - (.213F * amount);
            matrix.Matrix11 = .715F + (.285F * amount);
            matrix.Matrix21 = 1F - (matrix.Matrix01 + matrix.Matrix11);

            matrix.Matrix02 = .213F - (.213F * amount);
            matrix.Matrix12 = .715F - (.715F * amount);
            matrix.Matrix22 = 1F - (matrix.Matrix02 + matrix.Matrix12);
            matrix.Matrix33 = 1F;

            return matrix;
        }
    }
}