c# - 在上传到云之前压缩选取的图像大小 Xamarin

Question

我正在开发一个 Xamarin 应用程序，用户可以使用 Xamarin Essentials 插件选择图像。我现在的问题是在加载到云之前使用图像完整路径缩小图像大小。

编码

// Pick Image
    private async Task PickImages()
    {
        if (ImageCollection.Count >= 10)
        {
            ToastMessageLong("Cannot Select More then 10 Images.");
            return;
        }
        ImageLink image = new();
        try
        {
            FileResult result = await MediaPicker.PickPhotoAsync(new MediaPickerOptions
            {
                Title = "Pick an Image"
            });

            if (result == null) return;

            image.PostImages = result.FullPath;
            ImageCollection.Add(image);
        }
        catch (Exception x)
        {
            await DisplayAlert("", x.Message);
        }
    }


    private async Task UploadImagesToCloud()
    {
        if (ImageCollection.Count > 0)
        {
            List<ImageLink> imageLinks = new();
            foreach (ImageLink img in ImageCollection)
            {
                // Need to Compress Image before adding to cloud..

                ImageLink link = await CloudService.CS.UploadPostImage(img.PostImages);
                imageLinks.Add(link);
            }
            P.Images = imageLinks;
        }
    }

标签： c#xamarin

Answer 1

使用 SkiaSharp 给我的解决方案。

    public static string CreateThumbnail(string Path, string fileName)
    {
        var bitmap = SKBitmap.Decode(Path);
        int h = bitmap.Height;
        int w = bitmap.Width;
        int newWidth = w;
        int newHeight = h;
        //resize algorythm
        if (h > 1080 || w > 1080)
        {
            int rectHeight = 1080;
            int rectWidth = 1080;

            //aspect ratio calculation
            float W = w;
            float H = h;
            float aspect = W / H;

            //new dimensions by aspect ratio
            newWidth = (int)(rectWidth * aspect);
            newHeight = (int)(newWidth / aspect);

            //if one of the two dimensions exceed the box dimensions
            if (newWidth > rectWidth || newHeight > rectHeight)
            {
                //depending on which of the two exceeds the box dimensions set it as the box dimension and calculate the other one based on the aspect ratio
                if (newWidth > newHeight)
                {
                    newWidth = rectWidth;
                    newHeight = (int)(newWidth / aspect);
                }
                else
                {
                    newHeight = rectHeight;
                    newWidth = (int)(newHeight * aspect);
                }
            }
        }

        var resizedImage = bitmap.Resize(new SKImageInfo(newWidth, newHeight), SKBitmapResizeMethod.Lanczos3);
        var image = resizedImage.Encode(SKEncodedImageFormat.Jpeg, 80);
        var path = System.Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData);
        var filepath = System.IO.Path.Combine(path, fileName);
        string finalPath = filepath;
        using (var stream = File.OpenWrite(filepath))
            image.SaveTo(stream);
        return finalPath;
    }