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using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Documents;
using System.Windows.Media;
namespace HtmlToFlowDocument.Rendering
{
/// <summary>
/// Helper class for inverting colors of an existing <see cref="System.Windows.Documents.FlowDocument"/>.
/// </summary>
public class FlowDocumentColorInverter
{
/// <summary>
/// Inverts the colors of a FlowDocument recursively from leafes to root.
/// </summary>
/// <param name="parentElement">The parent element. Use a FlowDocument instance to invert the colors of the entire FlowDocument.</param>
public void InvertColorsRecursively(FrameworkContentElement parentElement)
{
if (null == parentElement)
return;
foreach (var child in WpfHelper.GetImmediateChildsOf(parentElement))
InvertColorsRecursively(child);
switch (parentElement)
{
case TextElement block:
if (block.ReadLocalValue(TextElement.ForegroundProperty) != DependencyProperty.UnsetValue)
{
block.Foreground = GetBrushWithInvertColors(block.Foreground);
}
if (block.ReadLocalValue(TextElement.BackgroundProperty) != DependencyProperty.UnsetValue)
{
block.Background = GetBrushWithInvertColors(block.Background);
}
break;
}
}
/// <summary>
/// Inverts the provided color.
/// </summary>
/// <param name="color">The color to invert.</param>
/// <returns>The inverted color.</returns>
public static Color InvertColor(Color color)
{
return Color.FromArgb(color.A, (byte)(255 - color.R), (byte)(255 - color.G), (byte)(255 - color.B));
}
/// <summary>
/// Inverts the color(s) of a brush.
/// </summary>
/// <param name="brush">The brush.</param>
/// <returns>A brush with inverted colors.</returns>
/// <exception cref="NotImplementedException"></exception>
public Brush GetBrushWithInvertColors(Brush brush)
{
if (null == brush)
return null;
switch (brush)
{
case SolidColorBrush solidColorBrush:
{
return GetBrushFromColor(solidColorBrush.Color);
}
case LinearGradientBrush linearGradientBrush:
{
var result = (LinearGradientBrush)linearGradientBrush.Clone();
for (int i = 0; i < result.GradientStops.Count; ++i)
result.GradientStops[i].Color = InvertColor(result.GradientStops[i].Color);
return result;
}
default:
return brush; // don't know how to invert a TileBrush or an ImageBrush
}
}
Dictionary<Color, Brush> _cachedSolidBrushes = new Dictionary<Color, System.Windows.Media.Brush>();
/// <summary>
/// Gets a solid color brush from the color specified.
/// </summary>
/// <param name="color">The color in RGBA format (A is the least significant byte).</param>
/// <returns>A solid color brush.</returns>
public System.Windows.Media.Brush GetBrushFromColor(Color color)
{
if (!_cachedSolidBrushes.TryGetValue(color, out var brush))
{
brush = new System.Windows.Media.SolidColorBrush(color);
brush.Freeze();
_cachedSolidBrushes.Add(color, brush);
}
return brush;
}
}
}
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