WPF 應用 - 顏色提取器

1. 功能

點擊色圖（以下圖）的某一點，獲取該點的顏色。

2. 實現

2.1 思路

1. 獲取圖片的像素數組，數組保存每一個點的 4 個通道，其中 3 個是 RGB 像素通道，1個是 Alpha 值
2. 獲取鼠標點擊點在色圖中的位置
3. 根據位置從像素數組中獲取 4 個通道值
4. 根據幾個通道值組成顏色值

2.2 代碼：

<Grid MouseLeftButtonDown="Grid_MouseLeftButtonDown">
    <Grid.RowDefinitions>
        <RowDefinition Height="20"/>
        <RowDefinition Height="auto"/>
        <RowDefinition Height="20"/>
        <RowDefinition Height="auto"/>
    </Grid.RowDefinitions>
    <Image Grid.Row="1" Source="/Resources/Images/Cars/colorpicker1.png" Width="320" Height="240"/>
    <Image Grid.Row="3" Source="/Resources/Images/Cars/BMW.jpg" Width="630" Height="457"/>
</Grid>

private void Grid_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
    if (e.Source.GetType() != typeof(Image)) return;
            
    var pos = e.GetPosition((Image)e.Source);
    var img = ((Image)e.Source).Source as BitmapSource;

    if (pos.X > 0 && pos.Y > 0 && pos.X < img.PixelWidth && pos.Y < img.PixelHeight)
        SampleImageClick(img, pos);
}

protected void SampleImageClick(BitmapSource img, Point pos)
{
    int stride = img.PixelWidth * 4;
    int size = img.PixelHeight * stride;
    byte[] pixels = new byte[(int)size];

    img.CopyPixels(pixels, stride, 0);

    // Get pixel
    var x = (int)pos.X;
    var y = (int)pos.Y;

    int index = y * stride + 4 * x;

    byte red = pixels[index];
    byte green = pixels[index + 1];
    byte blue = pixels[index + 2];
    byte alpha = pixels[index + 3];

    Color color = Color.FromArgb(alpha, blue, green, red);
    string ColorText =  "#" + color.A.ToString("X2") + color.R.ToString("X2") + color.G.ToString("X2") + color.B.ToString("X2");
}

參考：

https://social.msdn.microsoft.com/Forums/vstudio/en-US/82a5731e-e201-4aaf-8d4b-062b138338fe/getting-pixel-information-from-a-bitmapimage?forum=wpf