在Windows操作系统上以灰度方式打开屏幕

Question

我们能否在Windows操作系统(7,8,10)上使用GammaRamp(SetDeviceGammaRamp)将屏幕变成灰度？我需要这个来模拟电子墨水阅读器.我正在使用这个类来控制色温,并尝试使用以下因素实现将RGB图像转换为灰度的算法:red*0.2126; 绿色*0.7152; 我在本文中读到的蓝色*0.0722 .结果不是纯灰度.我不明白SetDeviceGammaRamp设置的gammaramp数组究竟是如何改变颜色的,这就是为什么不能实现灰度算法的原因.有关如何使用SetDeviceGammaRamp在此类中实现灰度转换的任何建议？

public static class GammaRamp
    {
        [DllImport("gdi32.dll")]
        private unsafe static extern bool SetDeviceGammaRamp(Int32 hdc, ushort* ramp);

        [DllImport("gdi32")]
        private unsafe static extern bool GetDeviceGammaRamp(Int32 hdc, ushort* ramp);

        private static Int32 hdc;

        public static unsafe void Set(int aBrightness, int aRed, int aGreen, int aBlue)
        {
            double red = 1, green = 1, blue = 1;

            red = (double)aRed / (double)255;
            green = (double)aGreen / (double)255;
            blue = (double)aBlue / (double)255;

            //Memory allocated through stackalloc is automatically free'd by the CLR.
            ushort* rgbArray = stackalloc ushort[768]; //3 * 256
            ushort* idx = rgbArray;

            for (int j = 0; j < 3; j++)
            {
                for (int i = 0; i < 256; i++)
                {
                    double arrayVal = (double)(i * (aBrightness + 128));

                    if (arrayVal > 65535)
                        arrayVal = (double)65535;

                    if (j == 0) //red
                        arrayVal = arrayVal * red * 0.2126;
                    else if (j == 1) //green
                        arrayVal = arrayVal * green * 0.7152;
                    else //blue
                        arrayVal = arrayVal * blue * 0.0722;

                    *idx = (ushort)arrayVal;
                    idx++;
                }
            }

            hdc = Graphics.FromHwnd(IntPtr.Zero).GetHdc().ToInt32();
            SetDeviceGammaRamp(hdc, rgbArray);
        }
}

如果不能使用GammaRamp我更喜欢它,因为它在Win 7,8和10中得到支持,我将使用一个新功能但仅适用于Windows 10

但要从WPF应用程序控制此设置,我必须更改以下注册表项

计算机\ HKEY_CURRENT_USER\Software\Microsoft\ColorFiltering\Active = 1计算机\ HKEY_CURRENT_USER\Software\Microsoft\ColorFiltering\FilterType = 0

我可以很容易地做,但如何使Windows操作系统从注册表刷新这个新设置？这也是一个有用的答案.

最后我会说我知道MagSetColorEffect winAPI,如果没有办法使用GammaRamp或其他选项我将用于Windows 7,但它是最后一个选项,因为它需要启用Aero,这是一种限制.

Answer 1

不可能使用类似于SetDeviceGammaRamp制作灰度滤镜的功能,因为它们分别作用于每个颜色通道.该lpRamp参数设置视频卡使用的LUT将像素强度(因为它将保存在屏幕截图中)映射到传输强度(如将放置在VGA连接器中的引脚上).这主要是遗留API,不会影响屏幕截图,远程桌面或使用所有图形卡.

要制作灰度滤色器,必须从每个颜色通道中获取数据,然后将它们混合在一起.您可以选择应用加权函数,使结果图像更准确地反映人类感知.

您可以使用您在该MagSetFullscreenColorEffect功能中指定的缩放系数(大多数运行Windows 8或更高版本的PC以及绝大多数Windows 7 PC上都可用).我目前无法访问FCU机器,但我怀疑设置中的新选项只是调用MagSetFullscreenColorEffect.

MagSetFullscreenColorEffect采用颜色矩阵,允许您转换RGBX的四个空间.您可以在MSDN或许多其他地方了解转换矩阵. ColorMatrix Viewer(GitHub)是测试和调整这些颜色矩阵的绝佳工具.

有关如何使用MagSetFullscreenColorEffect此示例的示例,请参阅以下示例.

C++:

#include <magnification.h>
#pragma comment(lib, "magnification.lib")

float redScale = 0.2126f, greenScale = 0.7152f, blueScale = 0.0722f;
MAGCOLOREFFECT magEffectInvert =
{ 
    { 
        { redScale,   redScale,   redScale,   0.0f,  0.0f },
        { greenScale, greenScale, greenScale, 0.0f,  0.0f },
        { blueScale,  blueScale,  blueScale,  0.0f,  0.0f },
        { 0.0f,       0.0f,       0.0f,       1.0f,  0.0f },
        { 0.0f,       0.0f,       0.0f,       0.0f,  1.0f }
    }
};

MagInitialize();
if (!MagSetFullscreenColorEffect(&magEffectInvert))
{
    std::cout << "Failed " << GetLastError() << std::endl;
}
system("pause");
MagUninitialize();

C#:

using System;
using System.Runtime.InteropServices;

namespace ManagedColorPlayground
{
    using static NativeMethods;

    class Program
    {
        static void Main(string[] args)
        {
            float redScale = 0.2126f, greenScale = 0.7152f, blueScale = 0.0722f;
            var magEffectInvert = new MAGCOLOREFFECT {
                transform = new [] {
                    redScale,   redScale,   redScale,   0.0f,  0.0f,
                    greenScale, greenScale, greenScale, 0.0f,  0.0f,
                    blueScale,  blueScale,  blueScale,  0.0f,  0.0f,
                    0.0f,       0.0f,       0.0f,       1.0f,  0.0f,
                    0.0f,       0.0f,       0.0f,       0.0f,  1.0f
                }
            };

            MagInitialize();
            MagSetFullscreenColorEffect(ref magEffectInvert);
            Console.ReadLine();
            MagUninitialize();
        }
    }

    static class NativeMethods
    {
        const string Magnification = "Magnification.dll";

        [DllImport(Magnification, ExactSpelling = true, SetLastError = true)]
        public static extern bool MagInitialize();

        [DllImport(Magnification, ExactSpelling = true, SetLastError = true)]
        public static extern bool MagUninitialize();

        [DllImport(Magnification, ExactSpelling = true, SetLastError = true)]
        public static extern bool MagSetFullscreenColorEffect(ref MAGCOLOREFFECT pEffect);

        public struct MAGCOLOREFFECT
        {
            [MarshalAs(UnmanagedType.ByValArray, SizeConst = 25)]
            public float[] transform;
        }
    }
}

之前MagSetFullscreenColorEffect:

之后MagSetFullscreenColorEffect: