图像绘制与存储技术解析

### 图像绘制与存储技术解析 在图像处理的领域中，涉及到众多关键技术，如色彩模式转换、图像绘制以及文件的读写操作等。下面将详细介绍这些技术的实现原理和代码示例。 #### 色彩模式转换与海报风格处理 在海报风格处理和单色转换的程序中，通过一系列的逻辑操作实现了色彩模式的转换。程序中定义了三个字节数组掩码，分别对应蓝色、绿色和红色通道。这些掩码用于对图像的像素进行处理，以达到特定的色彩效果。 ```csharp public sealed partial class MainPage : Page { // 掩码用于蓝色、绿色和红色 byte[] masks = { 0xFF, 0xFF, 0xFF }; void OnRadioButtonChecked(object sender, RoutedEventArgs args) { // 解码RadioButton的Tag属性 RadioButton radio = sender as RadioButton; string tag = radio.Tag as string; int maskIndex = -1; int bits = Int32.Parse(tag[1].ToString()); // 范围从1到8 byte mask = (byte)(0xFF << 8 - bits); bool needsUpdate; // 确定掩码数组中的索引 switch (tag[0]) { case 'r': maskIndex = 2; break; case 'g': maskIndex = 1; break; case 'b': maskIndex = 0; break; } // “All”按钮设置该行的其他切换按钮 if (tag[0] == 'a') { needsUpdate = masks[0] != mask && masks[1] != mask && masks[2] != mask; if (needsUpdate) masks[0] = masks[1] = masks[2] = mask; foreach (UIElement child in (radio.Parent as Panel).Children) { if (child != radio && Grid.GetRow(child as FrameworkElement) == Grid.GetRow(radio)) { (child as RadioButton).IsChecked = true; } } } else { needsUpdate = masks[maskIndex] != mask; if (needsUpdate) masks[maskIndex] = mask; } if (needsUpdate) UpdateBitmap(); } void OnCheckBoxChecked(object sender, RoutedEventArgs args) { UpdateBitmap(); } void UpdateBitmap() { if (bitmap == null) return; for (int index = 0; index < srcPixels.Length; index += 4) { // 对源像素应用掩码 byte B = (byte)(masks[0] & srcPixels[index + 0]); byte G = (byte)(masks[1] & srcPixels[index + 1]); byte R = (byte)(masks[2] & srcPixels[index + 2]); byte A = srcPixels[index + 3]; // 可能转换为灰度 if (monochromeCheckBox.IsChecked.Value) B = G = R = (byte)(0.30 * R + 0.59 * G + 0.11 * B); // 保存最终像素 dstPixels[index + 0] = B; dstPixels[index + 1] = G; dstPixels[index + 2] = R; dstPixels[index + 3] = A; } // 更新图像 pixelStream.Seek(0, SeekOrigin.Begin); pixelStream.Write(dstPixels, 0, dstPixels.Length); bitmap.Invalidate(); } } ``` 上述代码展示了如何处理 `RadioButton` 和 `CheckBox` 的事件，以及如何根据用户的选择更新图像的像素数据。`OnRadioButtonChecked` 方法根据 `RadioButton` 的 `Tag` 属性确定要更新的掩码，并在需要时更新图像。`OnCheckBoxChecked` 方法在复选框状态改变时调用 `UpdateBitmap` 方法。`UpdateBitmap` 方法则对图像的每个像素应用掩码，并根据是否选择单色模式进行灰度转换。 #### 图像绘制与保存 在图像绘制方面，传统的 `WritableBitmap` 对于 Windows Runtime 不支持直接绘制 `Line` 和 `Path` 等元素，因此需要实现自定义的绘制算法。下面是一些关键的结构体和接口，用于实现线条和弧线的绘制。 ```csharp // 几何线段接口 public interface IGeometrySegment { void GetAllX(double y, IList<double> xCollection); } // 线段结构体 public struct LineSegment : IGeometrySegment { readonly Point point1, point2; readonly double a, b; // 对应 x = ay + b public LineSegment(Point point1, Point point2) : this() { this.point1 = point1; this.point2 = point2; a = (point2.X - point1.X) / (point2.Y - point1.Y); b = point1.X - a * point1.Y; } public void GetAllX(double y, IList<double> xCollection) { if ((point2.Y > point1.Y && y >= point1.Y && y < point2.Y) || (point2.Y < point1.Y && y <= point1.Y && y > point2.Y)) { xCollection.Add(a * y + b); } } } // 弧线结构体 public struct ArcSegment : IGeometrySegment { readonly Point center, point1, point2; readonly double radius; readonly double angle1, angle2; public ArcSegment(Point center, double radius, Point point1, Point point2) : this() { this.center = center; this.radius = radius; this.point1 = point1; this.point2 = point2; this.angle1 = Math.Atan2(point1.Y - center.Y, point1.X - center.X); this.angle2 = Math.Atan2(point2.Y - center.Y, point2.X - center.X); } public void GetAllX(double y, IList<double> xCollection) { double sqrtArg = radius * radius - Math.Pow(y - center.Y, 2); if (sqrtArg >= 0) { double sqrt = Math.Sqrt(sqrtArg); TryY(y, center.X + sqrt, xCollection); TryY(y, center.X - sqrt, xCollection); } } void TryY(double y, double x, IList<double> xCollection) { double angle = Math.Atan2(y - center.Y, x - center.X); if ((angle1 < angle2 && (angle1 <= angle && angle < angle2)) || (angle1 > angle2 && (angle1 <= angle || angle < angle2))) { xCollection.Add((float)x); } } } // 圆形端点线段结构体 public struct RoundCappedLine : IGeometrySegment { LineSegment lineSegment1; ArcSegment arcSegment1; LineSegment lineSegment2; ArcSegment arcSegment2; public RoundCappedLine(Point point1, Point point2, double radius) : this() { Vector2 vector = new Vector2(point2 - new Vector2(point1)); Vector2 normVect = vector; normVect = normVect.Normalized; Point pt1a = point1 + radius * new Vector2(normVect.Y, -normVect.X); Point pt2a = pt1a + vector; Point pt1b = point1 + radius * new Vector2(-normVect.Y, normVect.X); Point pt2b = pt1b + vector; lineSegment1 = new LineSegment(pt1a, pt2a); arcSegment1 = new ArcSegment(point2, radius, pt2a, pt2b); lineSegment2 = new LineSegment(pt2b, pt1b); arcSegment2 = new ArcSegment(point1, radius, pt1b, pt1a); } public void GetAllX(double y, IList<double> xCollection) { arcSegment1.GetAllX(y, xCollection); lineSegment1.GetAllX(y, xCollection); arcSegment2.GetAllX(y, xCollection); lineSegment2.GetAllX(y, xCollection); } } // 圆形端点路径结构体 public struct RoundCappedPath : IGeometrySegment { LineSegment lineSegment1; ArcSegment arcSegment1; LineSegment lineSegment2; ArcSegment arcSegment2; public RoundCappedPath(Point point1, Point point2, double radius1, double radius2) : this() { Point c0 = point1; Point c1 = point2; double r0 = radius1; double r1 = radius2; // 获取从 c1 到 c0 的向量 Vector2 vCenters = new Vector2(c0) - new Vector2(c1); // 获取长度和归一化版本 double d = vCenters.Length; vCenters = vCenters.Normalized; // 创建相对于 c0 的焦点 F double e = d * r0 / (r1 - r0); Point F = c0 + e * vCenters; // 确定角度和直角边长度 double alpha = 180 * Math.Asin(r0 / e) / Math.PI; double leg0 = Math.Sqrt(e * e - r0 * r0); double leg1 = Math.Sqrt((e + d) * (e + d) - r1 * r1); // 切线向量 Vector2 vRight = -vCenters.Rotate(alpha); Vector2 vLeft = -vCenters.Rotate(-alpha); // 确定切点 Point t0R = F + leg0 * vRight; Point t0L = F + leg0 * vLeft; Point t1R = F + leg1 * vRight; Point t1L = F + leg1 * vLeft; lineSegment1 = new LineSegment(t1R, t0R); arcSegment1 = new ArcSegment(c0, r0, t0R, t0L); lineSegment2 = new LineSegment(t0L, t1L); arcSegment2 = new ArcSegment(c1, r1, t1L, t1R); } public void GetAllX(double y, IList<double> xCollection) { arcSegment1.GetAllX(y, xCollection); lineSegment1.GetAllX(y, xCollection); arcSegment2.GetAllX(y, xCollection); lineSegment2.GetAllX(y, xCollection); } } ``` 这些结构体实现了 `IGeometrySegment` 接口，通过 `GetAllX` 方法计算在给定 `y` 坐标下与线段或弧线相交的 `x` 坐标。`LineSegment` 结构体用于表示直线段，`ArcSegment` 结构体用于表示弧线，`RoundCappedLine` 结构体用于表示具有统一厚度的圆形端点线段，`RoundCappedPath` 结构体用于表示具有可变厚度的圆形端点路径。 在图像保存方面，程序需要处理文件的读写操作。以下是一个简单的流程图，展示了文件读写的主要流程： ```mermaid graph TD; A[开始] --> B[选择操作]; B --> C{打开文件}; C -- 是 --> D[读取文件内容]; C -- 否 --> E{保存文件}; E -- 是 --> F[写入文件内容]; E -- 否 --> G[结束]; D --> H[处理文件内容]; H --> I[显示或使用文件内容]; F --> J[确认保存成功]; J --> G; I --> G; ``` #### 图像文件的读写操作 在实际的程序中，需要处理图像文件的读写操作。以下是一些关键的代码示例，展示了如何创建新的位图、从文件加载位图以及保存位图到文件。 ```csharp public sealed partial class MainPage : Page { WriteableBitmap bitmap; Stream pixelStream; byte[] pixels; async Task CreateNewBitmapAndPixelArray() { bitmap = new WriteableBitmap((int)this.ActualWidth, (int)this.ActualHeight); pixels = new byte[4 * bitmap.PixelWidth * bitmap.PixelHeight]; // 用白色填充整个图像 for (int index = 0; index < pixels.Length; index++) pixels[index] = 0xFF; await InitializeBitmap(); appSettings.LoadedFilePath = null; appSettings.LoadedFilename = null; appSettings.IsImageModified = false; } async Task LoadBitmapFromFile(StorageFile storageFile) { using (IRandomAccessStreamWithContentType stream = await storageFile.OpenReadAsync()) { BitmapDecoder decoder = await BitmapDecoder.CreateAsync(stream); BitmapFrame bitmapframe = await decoder.GetFrameAsync(0); PixelDataProvider dataProvider = await bitmapframe.GetPixelDataAsync(BitmapPixelFormat.Bgra8, BitmapAlphaMode.Premultiplied, new BitmapTransform(), ExifOrientationMode.RespectExifOrientation, ColorManagementMode.ColorManageToSRgb); pixels = dataProvider.DetachPixelData(); bitmap = new WriteableBitmap((int)bitmapframe.PixelWidth, (int)bitmapframe.PixelHeight); await InitializeBitmap(); } } async Task InitializeBitmap() { pixelStream = bitmap.PixelBuf ```