使用Xamarin相机如何提高捕获后的图像质量？

Question

我已经按照https://www.youtube.com/watch?v=GaizJhx-FVg上的教程来激活相机功能，但是在我捕获图像后，它的质量变得非常低。关于如何调整图像质量的任何想法？

这是相机功能代码：

using Android.App;
using Android.Widget;
using Android.OS;
using System;
using Android.Content;
using Android.Runtime;
using Android.Views;
using Android.Graphics;

namespace Interactive_Ringgit_Recognizer_Try
{
    [Activity(Label = "Interactive_Ringgit_Recognizer", MainLauncher = true)]
    public class MainActivity : Activity
    {
        ImageView imageView;

        protected override void OnCreate(Bundle savedInstanceState)
        {
            base.OnCreate(savedInstanceState);

            // Set our view from the "main" layout resource
            SetContentView(Resource.Layout.Main);

            var btnCamera = FindViewById<Button>(Resource.Id.btnCamera);
            imageView = FindViewById<ImageView>(Resource.Id.imageView);

            btnCamera.Click += BtnCamera_Click;
        }

        protected override void OnActivityResult(int requestCode,[GeneratedEnum] Result resultCode, Intent data)
        {
            base.OnActivityResult(requestCode, resultCode, data);
            Bitmap bitmap = (Bitmap)data.Extras.Get("data");
            imageView.SetImageBitmap(bitmap);
        }

        private void BtnCamera_Click(object sender, EventArgs e)
        {
            Intent intent = new Intent         (Android.Provider.MediaStore.ActionImageCapture);
            StartActivityForResult(intent, 0);
        }
    }
}

Answer 1

使用Xamarin相机如何提高捕获后的图像质量？

从相机拍摄照片时，您可以创建一个目录来保存照片，通过创建文件并将其Uri添加到意图中，相机应用程序会将生成的照片保存在此文件中。

public static class App {
    public static Java.IO.File _file;
    public static Java.IO.File _dir;     
    public static Bitmap bitmap;
}

private void TakeAPicture(object sender, EventArgs eventArgs)
{
    Intent intent = new Intent(MediaStore.ActionImageCapture);
    App._file = new File(App._dir, String.Format("myPhoto_{0}.jpg", Guid.NewGuid()));
    intent.PutExtra(MediaStore.ExtraOutput, Uri.FromFile(App._file));
    StartActivityForResult(intent, 0);
}

在OnActivityResult方法中，我们在设备图库中提供照片。然后，您可以调用辅助方法来调整要显示的图像的大小。

protected override void OnActivityResult(int requestCode, Result resultCode, Intent data)
{
    base.OnActivityResult(requestCode, resultCode, data);

    // Make it available in the gallery
    Intent mediaScanIntent = new Intent(Intent.ActionMediaScannerScanFile);
    Uri contentUri = Uri.FromFile(App._file);
    mediaScanIntent.SetData(contentUri);
    SendBroadcast(mediaScanIntent);

    // Display in ImageView. We will resize the bitmap to fit the display
    // Loading the full sized image will consume to much memory 
    // and cause the application to crash.

    int height = Resources.DisplayMetrics.HeightPixels;
    int width = _imageView.Height;
    App.bitmap = App._file.Path.LoadAndResizeBitmap(width, height);
    if (App.bitmap != null)
    {
        _imageView.SetImageBitmap(App.bitmap);
        App.bitmap = null;
    }

    // Dispose of the Java side bitmap.
    GC.Collect();
}

LoadAndResizeBitmap方法：

public static Bitmap LoadAndResizeBitmap(this string fileName, int width, int height)
{
    // First we get the dimensions of the file on disk
    BitmapFactory.Options options = new BitmapFactory.Options { InJustDecodeBounds = true };
    BitmapFactory.DecodeFile(fileName, options);

    // Next we calculate the ratio that we need to resize the image by
    // in order to fit the requested dimensions.
    int outHeight = options.OutHeight;
    int outWidth = options.OutWidth;
    int inSampleSize = 1;

    if (outHeight > height || outWidth > width)
    {
        inSampleSize = outWidth > outHeight
                           ? outHeight / height
                           : outWidth / width;
    }

    // Now we will load the image and have BitmapFactory resize it for us.
    options.InSampleSize = inSampleSize;
    options.InJustDecodeBounds = false;
    Bitmap resizedBitmap = BitmapFactory.DecodeFile(fileName, options);

    return resizedBitmap;
}

对于完整的代码，您可以参考这个official document。