public static ImageFormat ToImageFormat(this KnownImageFormat knownImageFormat)
{
return(knownImageFormat switch
{
KnownImageFormat.Png => ImageFormat.Png,
KnownImageFormat.Jpeg => ImageFormat.Jpeg,
KnownImageFormat.Bmp => ImageFormat.Bmp,
KnownImageFormat.Gif => ImageFormat.Gif,
KnownImageFormat.Tiff => ImageFormat.Tiff,
KnownImageFormat.Wmf => ImageFormat.Wmf,
KnownImageFormat.Emf => ImageFormat.Emf,
KnownImageFormat.Icon => ImageFormat.Icon,
KnownImageFormat.Exif => ImageFormat.Exif,
_ => ImageFormat.Png
});
public async Task <IActionResult> Index(
int height = 100,
int width = 100,
KnownColor color = KnownColor.LightGray,
string text = "thumbnail",
KnownImageFormat format = KnownImageFormat.Png
)
{
var request = Request.QueryString.ToUriComponent();
var cacheKey = BitConverter.ToString(MD5.Create().ComputeHash(Encoding.UTF8.GetBytes(request)));
var(data, contentType, name) =
await _placeholderLogic.Resolve(height, width, color, text, format, cacheKey);
return(File(data, contentType, name));
}
public async Task <(byte[] file, string contentType, string name)> Resolve(int height, int width, KnownColor color,
string text,
KnownImageFormat format, string cacheKey)
{
var contentType = format.ToContentType();
var name = $"thumbnail.{contentType.Split('/')[1]}";
var fontSize = Math.Max(height, width) / 10;
var response = await _cache.GetAsync <byte[]>(cacheKey);
if (response.HasValue)
{
return(response.Value, contentType, name);
}
var bitmap = new Bitmap(width, height);
using var gfx = Graphics.FromImage(bitmap);
using var brush = new SolidBrush(Color.FromKnownColor(color));
using var arialFont = new Font("Arial", fontSize);
gfx.FillRectangle(brush, 0, 0, width, height);
var stringFormat = new StringFormat
{
LineAlignment = StringAlignment.Center,
Alignment = StringAlignment.Center
};
gfx.DrawString(text, arialFont, Brushes.Black, (float)(width / 2.0), (float)(height / 2.0), stringFormat);
var stream = new MemoryStream();
bitmap.Save(stream, format.ToImageFormat());
var bytes = stream.ToArray();
await _cache.SetAsync(cacheKey, bytes, TimeSpan.FromMinutes(5));
return(bytes, contentType, name);
}
public void SaveImageToFile(string filePath, Bitmap image, KnownImageFormat format)
{
using (var fileStream = new FileStream(filePath, FileMode.Create))
{
ImageFormat finalFormat = ImageFormat.Png;
switch (format)
{
case KnownImageFormat.png:
{
finalFormat = ImageFormat.Png;
break;
}
case KnownImageFormat.bmp:
{
finalFormat = ImageFormat.Bmp;
break;
}
case KnownImageFormat.gif:
{
finalFormat = ImageFormat.Gif;
break;
}
case KnownImageFormat.jpeg:
{
finalFormat = ImageFormat.Jpeg;
break;
}
default:
{
finalFormat = ImageFormat.Png;
break;
}
}
image.Save(fileStream, finalFormat);
}
}
