Xamarin旋转用相机捕获的图像

Question

我试图在skiasharp中获得一个图像，该图像左旋转90度以居中并完美地适合画布。我试过两种方法。我自己的定制方式，另一个似乎是一个流行的解决方案，但也许我不明白它是如何正确工作的?

1. 我行我素

代码如下:

SKSurface surf = e.Surface;
SKCanvas canvas = surf.Canvas;
SKSize size = canvasView.CanvasSize;
canvas.Clear();
SKRect rect = SKRect.Create(0.0f, 0.0f, size.Height, size.Width);
canvas.RotateDegrees(85);
canvas.DrawBitmap(m_bm, rect);

"m_bm"是在单独函数中检索的位图。该函数是:

// Let user take a picture.
var result = await MediaPicker.CapturePhotoAsync(new MediaPickerOptions
{
Title = "Take a picture"
});
// Save stream.
var stream = await result.OpenReadAsync();
// Create the bitmap.
m_bm = SKBitmap.Decode(stream);
// Set to true because the image will be prepared soon.
m_displayedImage = true;

我只放了85而不是90，因为我想从视觉上看到它越来越近，但当我这样做时，它从屏幕上消失了。我具有游戏编程背景，所以这通常是通过获取我们正在处理的任何东西(如游戏中的玩家)的宽度并将其添加到x位置来解决的。但是对于Xamarin，没有效果。这是我自己的尝试。然后我上网寻求帮助，他们给了我一个不同的实现。

流行的解决方案。

请看这里这个流行的解决方案，它是这个用户问题的第一个答案。我使用的代码略有不同，因为我没有看到在用户函数中返回图像的意义。

// Save stream.
var stream = await result.OpenReadAsync();
using (var bitmap = SKBitmap.Decode(stream))
{
var rotated = new SKBitmap(bitmap.Height, bitmap.Width);
using (var surface = new SKCanvas(rotated))
{
surface.Clear();
surface.Translate(rotated.Height, rotated.Width);
surface.RotateDegrees(90);
surface.DrawBitmap(bitmap, 0, 0);
}
}

我正在用画布绘制位图，我认为这会起作用，因为在其他代码样本中测试它，它确实是这样做的，所以我肯定没有正确旋转或什么?

Answer 1

@Cheesebaron在回复原始帖子时给我的链接最终成功了。但是一个新的问题出现了，我自己去谷歌一下。下面是我自己的代码:

namespace BugApp
{

public partial class MainPage : ContentPage
{
// Save bitmaps for later use.
static SKBitmap m_bm;
static SKBitmap m_editedBm;
// Boolean for displaying the image captured with the camera.
bool m_displayedImage;

public MainPage()
{
// Set to explicit default values to always be in control of the assignments.
m_bm = null;
m_editedBm = null;
// No picture has been taken yet.
m_displayedImage = false;
InitializeComponent();
}
// Assigned to the button in the xaml page.
private async void SnapPicture(Object sender, System.EventArgs e)
{
// Let user take a picture.
var result = await MediaPicker.CapturePhotoAsync(new MediaPickerOptions
{
Title = "Take a picture"
});
// Save stream.
var stream = await result.OpenReadAsync();
// Create the bitmap.
m_bm = SKBitmap.Decode(stream);
// Get the rotated image.
m_editedBm = Rotate();
// Set to true because the image will be prepared soon.
m_displayedImage = true;
}
public static SKBitmap Rotate()
{
using (var bitmap = m_bm)
{
var rotated = new SKBitmap(bitmap.Height, bitmap.Width);
using (var surface = new SKCanvas(rotated))
{
surface.Translate(bitmap.Width, 0);
surface.RotateDegrees(90);
surface.DrawBitmap(bitmap, 0, 0);
}
return rotated;
}
}
private void OnCanvasViewPaintSurface(object sender, SKPaintSurfaceEventArgs e)
{
if(m_bm != null && m_displayedImage == true)
{
e.Surface.Canvas.Clear();
// Draw in a new rect space.
e.Surface.Canvas.DrawBitmap(m_editedBm, new SKRect(0.0f, 0.0f, 300.0f, 300.0f));
// ---Testing.
// e.Surface.Canvas.DrawBitmap(m_editedBm, new SKRect(112, 238, 184, 310), new SKRect(0, 0, 9, 9));

// Avoid having this function launch again for now.
m_displayedImage = false;
}
}
}

}

重要的代码部分是rotate函数，也就是下面这个:

感谢所有回复的人。