ImageUtils.cs

using Microsoft.Extensions.Caching.Memory;
using SkiaSharp;

namespace EasyFortniteStats_ImageApi;

public class ImageUtils
{
    public static void BitmapPostEvictionCallback(object key, object? value, EvictionReason reason, object? state)
    {
        Console.WriteLine($"MemoryCache: Disposing {key} | Reason: {reason}");
        if (value is null) return;
        var bmp = (SKBitmap) value;
        bmp.Dispose();
    }

    public static async Task<SKBitmap> GenerateDiscordBox(SharedAssets _assets, string username,
        float resizeFactor = 1.0f)
    {
        var segoeFont = await _assets.GetFont("Assets/Fonts/Segoe.ttf"); // don't dispose

        using var discordTagTextPaint = new SKPaint();
        discordTagTextPaint.IsAntialias = true;
        discordTagTextPaint.Color = SKColors.White;
        discordTagTextPaint.Typeface = segoeFont;
        discordTagTextPaint.TextSize = 25 * resizeFactor;

        var discordTagTextBounds = new SKRect();
        discordTagTextPaint.MeasureText(username, ref discordTagTextBounds);

        var imageInfo = new SKImageInfo(
            (int) Math.Min(discordTagTextBounds.Width + (10 + 2 * 15 + 50) * resizeFactor, 459 * resizeFactor),
            (int) (62 * resizeFactor));
        var bitmap = new SKBitmap(imageInfo);
        using var canvas = new SKCanvas(bitmap);

        var discordBoxR = 15 * resizeFactor;
        using var discordBoxPaint = new SKPaint();
        discordBoxPaint.IsAntialias = true;
        discordBoxPaint.Color = new SKColor(88, 101, 242);
        canvas.DrawRoundRect(0, 0, imageInfo.Width, imageInfo.Height, discordBoxR, discordBoxR, discordBoxPaint);

        var logoResizeWidth = (int) (50 * resizeFactor);
        var discordLogoBitmap = await _assets.GetBitmap("Assets/Images/DiscordLogo.png"); // don't dispose
        // get height with the same aspect ratio
        var logoResizeHeight = (int) (discordLogoBitmap!.Height * (logoResizeWidth / (float) discordLogoBitmap.Width));
        var discordLogoBitmapResized =
            discordLogoBitmap.Resize(new SKImageInfo(logoResizeWidth, logoResizeHeight), SKFilterQuality.High);
        canvas.DrawBitmap(discordLogoBitmapResized, 10 * resizeFactor,
            (float) (imageInfo.Height - discordLogoBitmapResized.Height) / 2);

        while (discordTagTextBounds.Width + (10 + 2 * 15 + 50) * resizeFactor > imageInfo.Width)
        {
            discordTagTextPaint.TextSize--;
            discordTagTextPaint.MeasureText(username, ref discordTagTextBounds);
        }

        canvas.DrawText(username, (10 + 15) * resizeFactor + discordLogoBitmapResized.Width,
            (float) imageInfo.Height / 2 - discordTagTextBounds.MidY, discordTagTextPaint);

        return bitmap;
    }

    public static SKBitmap RotateBitmap(SKBitmap bitmap, float angle)
    {
        var radians = MathF.PI * angle / 180;
        var sine = MathF.Abs(MathF.Sin(radians));
        var cosine = MathF.Abs(MathF.Cos(radians));
        int originalWidth = bitmap.Width, originalHeight = bitmap.Height;
        var rotatedWidth = (int) (cosine * originalWidth + sine * originalHeight);
        var rotatedHeight = (int) (cosine * originalHeight + sine * originalWidth);

        var rotatedBitmap = new SKBitmap(rotatedWidth, rotatedHeight);
        using var rotatedCanvas = new SKCanvas(rotatedBitmap);
        rotatedCanvas.Clear();
        rotatedCanvas.Translate(rotatedWidth / 2f, rotatedHeight / 2f);
        rotatedCanvas.RotateDegrees(-angle);
        rotatedCanvas.Translate(-originalWidth / 2f, -originalHeight / 2f);
        rotatedCanvas.DrawBitmap(bitmap, SKPoint.Empty);

        return rotatedBitmap;
    }

    public static SKBitmap GenerateRarityStripe(int width, SKColor rarityColor)
    {
        var imageInfo = new SKImageInfo(width, 14);
        var bitmap = new SKBitmap(imageInfo);
        using var canvas = new SKCanvas(bitmap);

        using var paint = new SKPaint();
        {
            paint.IsAntialias = true;
            paint.Color = rarityColor;
            paint.Style = SKPaintStyle.Fill;

            using var path = new SKPath();
            path.MoveTo(0, imageInfo.Height - 5);
            path.LineTo(imageInfo.Width, 0);
            path.LineTo(imageInfo.Width, imageInfo.Height - 6);
            path.LineTo(0, imageInfo.Height);
            path.Close();

            canvas.DrawPath(path, paint);
        }

        return bitmap;
    }

    public static SKBitmap GenerateItemCardOverlay(int width, SKBitmap? icon = null)
    {
        var imageInfo = new SKImageInfo(width, 65);
        var bitmap = new SKBitmap(imageInfo);
        using var canvas = new SKCanvas(bitmap);

        using (var paint = new SKPaint())
        {
            paint.IsAntialias = true;
            paint.Color = new SKColor(14, 14, 14);
            paint.Style = SKPaintStyle.Fill;

            canvas.DrawRect(0, 0, imageInfo.Width, imageInfo.Height, paint);
        }

        if (icon is not null)
        {
            using var rotatedVbucksBitmap = RotateBitmap(icon, -20);
            using var resizedVBucksBitmap = rotatedVbucksBitmap.Resize(new SKImageInfo(47, 47), SKFilterQuality.Medium);

            canvas.DrawBitmap(resizedVBucksBitmap, new SKPoint(imageInfo.Width - 45, imageInfo.Height - 35));
        }

        using (var paint = new SKPaint())
        {
            paint.IsAntialias = true;
            paint.Color = new SKColor(30, 30, 30);
            paint.Style = SKPaintStyle.Fill;

            using var path = new SKPath();
            path.MoveTo(0, imageInfo.Height - 29);
            path.LineTo(imageInfo.Width, imageInfo.Height - 29);
            path.LineTo(imageInfo.Width, imageInfo.Height - 25);
            path.LineTo(0, imageInfo.Height - 24);
            path.Close();

            canvas.DrawPath(path, paint);

            canvas.DrawRect(0, 0, imageInfo.Width, imageInfo.Height - 29, paint);
        }

        return bitmap;
    }

    public static SKColor ParseColor(string hexString)
    {
        var span = hexString.AsSpan();
        var offset = span[0] == '#' ? 1 : 0;

        if (hexString.Length - offset == 8)
        {
            hexString = string.Concat(span.Slice(6 + offset, 2), span.Slice(0 + offset, 6));
        }
        return SKColor.Parse(hexString);
    }
}