SkiaSharp 触摸位图图像

如何解决SkiaSharp 触摸位图图像

在应用程序中，我试图开发的一个关键部分是获取用户触摸的位置。起初我想使用点击手势识别器，但在快速谷歌搜索后我发现这是无用的（参见 here 示例）。

然后我相信我发现了 SkiaSharp 并且在学习如何使用它之后，至少在某种程度上，我仍然不确定我如何获得正确的触摸坐标。以下是我项目中与问题相关的代码部分。

画布触控功能

 private void canvasView_Touch(object sender,SKTouchEventArgs e)
 {
     // Only carry on with this function if the image is already on screen.
     if(m_isImagedisplayed)
     {
         // Use switch to get what type of action occurred.
         switch (e.ActionType)
         {
             case SKTouchAction.pressed:
                 TouchImage(e.Location);

                 // Update simply tries to draw a small square using double for loops.
                 m_editedBm = Update(sender);

                 // Refresh screen.
                 (sender as SKCanvasView).InvalidateSurface();
                 break;
             default:
                 break;
         }
     }
 }

触摸图片

 private void TouchImage(SKPoint point)
 {
     // Is the point in range of the canvas?
     if(point.X >= m_x && point.X <= (m_editedCanvasSize.Width + m_x) &&
         point.Y >= m_y && point.Y <= (m_editedCanvasSize.Height + m_y))
     {
         // Save the point for later and set the boolean to true so the algorithm can begin.
         m_clickPoint = point;

         m_updatealgorithm = true;
     }
 }

在这里，我只是查看或尝试查看单击的点是否在图像范围内，并且我创建了一个不同的 SkSize 变量来提供帮助。忽略布尔值，没那么重要。

更新函数（尝试在按下的点上绘制的函数，因此它是最重要的）

 public SKBitmap Update(object sender) 
 {
     // Create the default test color to replace current pixel colors in the bitmap.
     SKColor color = new SKColor(255,255,255);

     // Create a new surface with the current bitmap.
     using (var surface = new SKCanvas(m_editedBm))
     {
         /* According to this:  https://docs.microsoft.com/en-us/xamarin/xamarin-forms/user-interface/graphics/skiasharp/paths/finger-paint,the points I have to start are in Xamarin forms coordinates,but I need to translate them to SkiaSharp coordinates which are in
           pixels. */
         Point pt = new Point((double)m_touchPoint.X,(double)m_touchPoint.Y);
         SKPoint newPoint = ConvertToPixel(pt);

         // Loop over the touch point start,then go to a certain value (like x + 100) just to get a "block" that's been altered for pixels.
         for (int x = (int)newPoint.X; x < (int)newPoint.X + 200.0f; ++x)
         {
             for (int y = (int)newPoint.Y; y < (int)newPoint.Y + 200.0f; ++y)
             {
                 // According to the x and y,change the color.
                 m_editedBm.SetPixel(x,y,color);
             }
         }

         return m_editedBm;
     }
 }

在这里，我想它会在我按下的坐标处开始（并且由于“TouchImage”功能，这些坐标已被确认在图像范围内。当它确实得到正确的坐标（或至少应该这样做）正方形将一次绘制一条“线”。我有游戏编程背景，所以这种听起来很简单，但我不敢相信我没有得到这个第一次就对了。

我还有另一个功能，它可能被证明是值得的，因为原始图像被旋转然后放在屏幕上。为什么？好吧，默认情况下，图像在拍摄后显示，然后向左旋转。我不知道为什么，但我用以下功能纠正了它：

    // Just rotate the image because for some reason it's titled 90 degrees to the left.
    public static SKBitmap Rotate()
    {
        using (var bitmap = m_bm)
        {
            // The new ones width IS the old ones height. 
            var rotated = new SKBitmap(bitmap.Height,bitmap.Width);

            using (var surface = new SKCanvas(rotated))
            {
                surface.Translate(rotated.Width,0.0f);
                surface.Rotatedegrees(90);
                surface.DrawBitmap(bitmap,0);
            }

            return rotated;
        }
    }

我会继续阅读和查找有关我做错了什么的东西，但如果能得到任何帮助，我将不胜感激。