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using SkiaSharp;
using Xunit;
namespace Jellyfin.Drawing.Skia.Tests;
/// <summary>
/// Covers what <see cref="SkiaEncoder.ResizeImage"/> does either side of a resize: at matching
/// dimensions it must not touch the image at all, and sharpening belongs to downscales only.
/// </summary>
public class SkiaEncoderResizeTests
{
private static SKBitmap CreateEdgeBitmap(int width, int height)
{
var bitmap = new SKBitmap(new SKImageInfo(width, height, SKColorType.Rgba8888, SKAlphaType.Premul));
using var canvas = new SKCanvas(bitmap);
canvas.Clear(new SKColor(40, 60, 80));
using var paint = new SKPaint { Color = new SKColor(220, 210, 200) };
canvas.DrawRect(SKRect.Create(0, 0, width / 2f, height), paint);
return bitmap;
}
private static SKImageInfo InfoFor(SKBitmap source, int width, int height)
=> new SKImageInfo(width, height, source.ColorType, source.AlphaType, source.ColorSpace);
/// <summary>
/// Draws without sharpening, which is what the resize is expected to reduce to when it is not
/// downscaling.
/// </summary>
private static SKBitmap DrawOnly(SKBitmap source, SKImageInfo targetInfo, SKSamplingOptions sampling)
{
var target = new SKBitmap(targetInfo);
using var canvas = new SKCanvas(target);
using var paint = new SKPaint();
canvas.DrawBitmap(
source,
SKRect.Create(0, 0, source.Width, source.Height),
SKRect.Create(0, 0, targetInfo.Width, targetInfo.Height),
sampling,
paint);
return target;
}
private static void AssertSamePixels(SKBitmap expected, SKBitmap actual)
{
Assert.Equal(expected.Width, actual.Width);
Assert.Equal(expected.Height, actual.Height);
for (var y = 0; y < expected.Height; y++)
{
for (var x = 0; x < expected.Width; x++)
{
Assert.Equal(expected.GetPixel(x, y), actual.GetPixel(x, y));
}
}
}
[Fact]
public void ResizeImage_MatchingDimensions_ReturnsTheImageUntouched()
{
using var source = CreateEdgeBitmap(16, 16);
using var result = SkiaEncoder.ResizeImage(source, InfoFor(source, 16, 16));
using var resultBitmap = SKBitmap.FromImage(result);
// Unsharpened, so the edge is still exactly where it was.
AssertSamePixels(source, resultBitmap);
}
[Fact]
public void ResizeImage_Upscale_DoesNotSharpen()
{
using var source = CreateEdgeBitmap(8, 8);
var targetInfo = InfoFor(source, 24, 24);
using var result = SkiaEncoder.ResizeImage(source, targetInfo);
using var resultBitmap = SKBitmap.FromImage(result);
using var expected = DrawOnly(source, targetInfo, SkiaEncoder.UpscaleSamplingOptions);
AssertSamePixels(expected, resultBitmap);
}
[Fact]
public void ResizeImage_Downscale_StillSharpens()
{
using var source = CreateEdgeBitmap(32, 32);
var targetInfo = InfoFor(source, 16, 16);
using var result = SkiaEncoder.ResizeImage(source, targetInfo);
using var resultBitmap = SKBitmap.FromImage(result);
using var unsharpened = DrawOnly(source, targetInfo, SkiaEncoder.DefaultSamplingOptions);
using var sharpened = DrawOnly(source, targetInfo, SkiaEncoder.DefaultSamplingOptions);
SkiaEncoder.SharpenInPlace(sharpened);
AssertSamePixels(sharpened, resultBitmap);
// Guards the test itself: the edge has to be something sharpening actually changes.
Assert.NotEqual(unsharpened.GetPixel(8, 8), sharpened.GetPixel(8, 8));
}
}
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