本文告诉大家如何修改图片的颜色，如去掉图片的蓝色
在 WPF 可以使用很多图片处理的方法，本文告诉大家的是一个图片处理，可以把处理的图片保存在文件。
在阅读本文，我假设大家是熟悉 WPF 的，至少了解 C# ，也知道图片的格式。
在 WPF 可以使用 ARBG 数组表示图片，本文修改图片颜色的方法就是使用 ARBG 数组的方法修改，修改里面的元素的值。
如我需要去掉图片的蓝色，就可以通过修改 ARBG 数组的元素，设置所有蓝色为 0 ，去掉蓝色。
读取图片
首先找到一张好看的图片，放在解决方案
读取解决方案的图片
var stream = Application.GetResourceStream(new Uri("pack://application:,,,/1.jpg")).Stream;
如果找不到图片，就是没有设置图片生成是 Resource
解析文件
创建 WriteableBitmap 需要使用 ImageSource 所以需要先解析
// 其他忽略代码
var bitmapImage = new BitmapImage();
bitmapImage.BeginInit();
bitmapImage.StreamSource = stream;
bitmapImage.EndInit();
使用 BitmapImage 解析文件
创建图片
在读取图片之后就可以创建图片
var writeableBitmap = new WriteableBitmap(bitmapImage);
转换图片格式
如果读取到的图片不是 BGRA 的格式，就需要转换图片格式
var formatConvertedBitmap = new FormatConvertedBitmap();
formatConvertedBitmap.BeginInit();
formatConvertedBitmap.Source = bitmapImage;
formatConvertedBitmap.DestinationFormat = PixelFormats.Bgra32;
formatConvertedBitmap.EndInit();
使用这个代码可以把格式转为PixelFormats.Bgra32，需要重新创建图片
var stream = Application.GetResourceStream(new Uri("pack://application:,,,/1.jpg")).Stream;
var bitmapImage = new BitmapImage();
bitmapImage.BeginInit();
bitmapImage.StreamSource = stream;
bitmapImage.EndInit();
var formatConvertedBitmap = new FormatConvertedBitmap();
formatConvertedBitmap.BeginInit();
formatConvertedBitmap.Source = bitmapImage;
formatConvertedBitmap.DestinationFormat = PixelFormats.Bgra32;
formatConvertedBitmap.EndInit();
var writeableBitmap = new WriteableBitmap(formatConvertedBitmap);
尝试显示图片，可以看到图片还是很好看
读取数组
在图片可以看到图片是使用 BGRA 的格式数组，所以只需要读取图片数组就可以修改图片
读取图片需要使用不安全代码，需要右击项目属性，点击生成，允许不安全代码。
在修改图片之前需要使用 Lock 函数，读取图片的数组长度可以使用这个代码
var length = writeableBitmap.PixelWidth * writeableBitmap.PixelHeight *
writeableBitmap.Format.BitsPerPixel / 8;
这里知道使用的是 BGRA 也就是一个像素使用 4 个 byte ，一个图片的像素就是writeableBitmap.PixelWidth * writeableBitmap.PixelHeight 。这里 writeableBitmap.Format.BitsPerPixel 就是拿到一个像素的 bit 数。
转换数组
var backBuffer = (byte*) writeableBitmap.BackBuffer;
读取颜色就是从数组拿到值
for (int i = 0; i + 4 < length; i = i + 4)
{
var blue = backBuffer[i];
var green = backBuffer[i + 1];
var red = backBuffer[i + 2];
var alpha = backBuffer[i + 3];
}
修改颜色就是修改对应的值然后设置数组，如设置蓝色是 0 去掉蓝色
for (int i = 0; i + 4 < length; i = i + 4)
{
var blue = backBuffer[i];
var green = backBuffer[i + 1];
var red = backBuffer[i + 2];
var alpha = backBuffer[i + 3];
blue = 0;
backBuffer[i] = blue;
backBuffer[i + 1] = green;
backBuffer[i + 2] = red;
backBuffer[i + 3] = alpha;
}
设置之后需要设置图片显示
writeableBitmap.AddDirtyRect(new Int32Rect(0, 0, writeableBitmap.PixelWidth, writeableBitmap.PixelHeight));
writeableBitmap.Unlock();
所以去掉图片的蓝色可以使用 RemoveBlue 函数，设置蓝色为 0 的方法就是读取蓝色然后修改数组
private unsafe void RemoveBlue(WriteableBitmap writeableBitmap)
{
writeableBitmap.Lock();
var length = writeableBitmap.PixelWidth * writeableBitmap.PixelHeight *
writeableBitmap.Format.BitsPerPixel / 8;
var backBuffer = (byte*) writeableBitmap.BackBuffer;
for (int i = 0; i + 4 < length; i = i + 4)
{
var blue = backBuffer[i];
var green = backBuffer[i + 1];
var red = backBuffer[i + 2];
var alpha = backBuffer[i + 3];
blue = 0;
backBuffer[i] = blue;
backBuffer[i + 1] = green;
backBuffer[i + 2] = red;
backBuffer[i + 3] = alpha;
}
writeableBitmap.AddDirtyRect(new Int32Rect(0, 0, writeableBitmap.PixelWidth, writeableBitmap.PixelHeight));
writeableBitmap.Unlock();
}
去掉蓝色的图片
现在的程序看起来还不能使用，尝试添加几个依赖属性，用来修改图片的颜色
可以点击这里下载程序
首先在 xaml 添加几个控件
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="485*" />
<ColumnDefinition Width="308*" />
</Grid.ColumnDefinitions>
<Image x:Name="Image" />
<Grid Grid.Column="1">
<Grid VerticalAlignment="Center">
<FrameworkElement.Resources>
<Style TargetType="Slider">
<Setter Property="Width" Value="100" />
<Setter Property="HorizontalAlignment" Value="Center" />
<Setter Property="Margin" Value="10,10,10,10" />
<Setter Property="Minimum" Value="-255" />
<Setter Property="Maximum" Value="255" />
</Style>
<Style TargetType="TextBlock">
<Setter Property="Margin" Value="10,10,10,10" />
<Setter Property="HorizontalAlignment" Value="Center" />
</Style>
<local:DoubleConvert x:Key="DoubleConvert" />
</FrameworkElement.Resources>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="Auto" />
<ColumnDefinition Width="Auto" />
<ColumnDefinition Width="Auto" />
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition Height="Auto" />
<RowDefinition Height="Auto" />
<RowDefinition Height="Auto" />
<RowDefinition Height="Auto" />
</Grid.RowDefinitions>
<TextBlock>蓝色</TextBlock>
<TextBlock Grid.Row="1" Grid.Column="0">绿色</TextBlock>
<TextBlock Grid.Row="2" Grid.Column="0">红色</TextBlock>
<TextBlock Grid.Row="3" Grid.Column="0">透明度</TextBlock>
<!-- 蓝色 -->
<Slider Grid.Row="0" Grid.Column="1" Value="{Binding Path=Blue,Mode=TwoWay}" />
<!-- 绿色 -->
<Slider Grid.Row="1" Grid.Column="1" Value="{Binding Path=Green,Mode=TwoWay}" />
<!-- 红色 -->
<Slider Grid.Row="2" Grid.Column="1" Value="{Binding Path=Red,Mode=TwoWay}" />
<!-- 透明度 -->
<Slider Grid.Row="3" Grid.Column="1" Value="{Binding Path=Alpha,Mode=TwoWay}" />
<!-- 蓝色 -->
<TextBlock Grid.Row="0" Grid.Column="2"
Text="{Binding Path=Blue,Mode=OneWay,Converter={StaticResource DoubleConvert}}" />
<!-- 绿色 -->
<TextBlock Grid.Row="1" Grid.Column="2"
Text="{Binding Path=Green,Mode=OneWay,Converter={StaticResource DoubleConvert}}" />
<!-- 红色 -->
<TextBlock Grid.Row="2" Grid.Column="2"
Text="{Binding Path=Red,Mode=OneWay,Converter={StaticResource DoubleConvert}}" />
<!-- 透明度 -->
<TextBlock Grid.Row="3" Grid.Column="2"
Text="{Binding Path=Alpha,Mode=OneWay,Converter={StaticResource DoubleConvert}}" />
</Grid>
<Grid VerticalAlignment="Bottom">
<Button Margin="10,10,10,10" Content="替换图片" Click="Button_OnClick" />
</Grid>
</Grid>
</Grid>
注意在页面设置数据
DataContext="{Binding RelativeSource={RelativeSource Self}}"
然后打开 cs 添加代码
private WriteableBitmap _writeableBitmap;
public MainWindow()
{
InitializeComponent();
Image.Margin = new Thickness(10, 10, 10, 10);
var stream = Application.GetResourceStream(new Uri("pack://application:,,,/1.jpg")).Stream;
ChangeImage(stream);
DataContext = this;
}
public static readonly DependencyProperty BlueProperty = DependencyProperty.Register(
"Blue", typeof(double), typeof(MainWindow),
new PropertyMetadata(default(double), (s, e) => ((MainWindow) s).ChangeArray()));
public double Blue
{
get { return (double) GetValue(BlueProperty); }
set { SetValue(BlueProperty, value); }
}
public static readonly DependencyProperty GreenProperty = DependencyProperty.Register(
"Green", typeof(double), typeof(MainWindow),
new PropertyMetadata(default(double), (s, e) => ((MainWindow) s).ChangeArray()));
public double Green
{
get { return (double) GetValue(GreenProperty); }
set { SetValue(GreenProperty, value); }
}
public static readonly DependencyProperty RedProperty = DependencyProperty.Register(
"Red", typeof(double), typeof(MainWindow),
new PropertyMetadata(default(double), (s, e) => ((MainWindow) s).ChangeArray()));
public double Red
{
get { return (double) GetValue(RedProperty); }
set { SetValue(RedProperty, value); }
}
public static readonly DependencyProperty AlphaProperty = DependencyProperty.Register(
"Alpha", typeof(double), typeof(MainWindow),
new PropertyMetadata(default(double), (s, e) => ((MainWindow) s).ChangeArray()));
public double Alpha
{
get { return (double) GetValue(AlphaProperty); }
set { SetValue(AlphaProperty, value); }
}
private void ChangeImage(Stream stream)
{
var bitmapImage = new BitmapImage();
bitmapImage.BeginInit();
bitmapImage.StreamSource = stream;
bitmapImage.EndInit();
var formatConvertedBitmap = new FormatConvertedBitmap();
formatConvertedBitmap.BeginInit();
formatConvertedBitmap.Source = bitmapImage;
formatConvertedBitmap.DestinationFormat = PixelFormats.Bgra32;
formatConvertedBitmap.EndInit();
_writeableBitmap = new WriteableBitmap(formatConvertedBitmap);
ChangeArray();
}
private unsafe void ChangeArray()
{
var writeableBitmap = _writeableBitmap;
if (writeableBitmap == null)
{
return;
}
writeableBitmap.Lock();
var length = writeableBitmap.PixelWidth * writeableBitmap.PixelHeight *
writeableBitmap.Format.BitsPerPixel / 8;
var backBuffer = (byte*) writeableBitmap.BackBuffer;
var byteList = new byte[length];
for (int i = 0; i + 4 < length; i = i + 4)
{
var blue = backBuffer[i];
var green = backBuffer[i + 1];
var red = backBuffer[i + 2];
var alpha = backBuffer[i + 3];
blue += (byte) Blue;
green += (byte) Green;
red += (byte) Red;
alpha += (byte) Alpha;
byteList[i] = blue;
byteList[i + 1] = green;
byteList[i + 2] = red;
byteList[i + 3] = alpha;
}
writeableBitmap.Unlock();
writeableBitmap = new WriteableBitmap(writeableBitmap.PixelWidth, writeableBitmap.PixelHeight, 96, 96,
writeableBitmap.Format, writeableBitmap.Palette);
writeableBitmap.Lock();
writeableBitmap.WritePixels(new Int32Rect(0, 0, writeableBitmap.PixelWidth, writeableBitmap.PixelHeight),
byteList, writeableBitmap.BackBufferStride, 0);
writeableBitmap.AddDirtyRect(new Int32Rect(0, 0, writeableBitmap.PixelWidth, writeableBitmap.PixelHeight));
writeableBitmap.Unlock();
Image.Source = writeableBitmap;
}
private void Button_OnClick(object sender, RoutedEventArgs e)
{
var openFileDialog = new OpenFileDialog();
openFileDialog.Filter = "jpg(*.jpg)|*.jpg";
if (openFileDialog.ShowDialog() == true)
{
var stream = openFileDialog.OpenFile();
ChangeImage(stream);
}
}
public class DoubleConvert : IValueConverter
{
/// <inheritdoc />
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
if (value is double n)
{
return n.ToString("0.00");
}
return DependencyProperty.UnsetValue;
}
/// <inheritdoc />
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
return null;
}
}
参见：
