SocialPub/PrivaPub.Tests/Domain/MediaProcessingTests.cs

using NetVips;

using PrivaPub.Domain.Media;

namespace PrivaPub.Tests.Domain
{
	public class MediaProcessingTests
	{
		static byte[] JpegWithMetadata(int width, int height)
		{
			using var image = (Image.Black(width, height, bands: 3) + new double[] { 200, 40, 90 }).Cast(Enums.BandFormat.Uchar);
			using var tagged = image.Mutate(m =>
			{
				m.Set(GValue.GStrType, "exif-ifd0-ImageDescription", "where I live");
				m.Set(GValue.GStrType, "exif-ifd0-Artist", "Alice Smith");
				m.Set(GValue.GStrType, "exif-ifd2-UserComment", "at home");
				m.Set(GValue.BlobType, "xmp-data", System.Text.Encoding.UTF8.GetBytes("<x:xmpmeta xmlns:x='adobe:ns:meta/'><secret/></x:xmpmeta>"));
			});
			return tagged.WriteToBuffer(".jpg");
		}

		// SVG, PDF and the other formats libvips could read never load from an upload, whatever it claims to be
		[Fact]
		public void Only_the_upload_formats_are_ever_loaded()
		{
			var svg = "<svg xmlns='http://www.w3.org/2000/svg' width='20000' height='20000'><rect width='10' height='10'/></svg>"u8.ToArray();
			Assert.Throws<VipsException>(() => MediaService.Inspect(svg));
			Assert.Throws<VipsException>(() => MediaService.Inspect("%PDF-1.4\n1 0 obj<<>>endobj\ntrailer<<>>\n%%EOF"u8.ToArray()));
			using var colour = (Image.Black(8, 8, bands: 3) + 100).Cast(Enums.BandFormat.Uchar);
			foreach (var format in new[] { ".jpg", ".png", ".gif", ".webp" })
				Assert.Equal(8, MediaService.Inspect(colour.WriteToBuffer(format)).Width);
			Assert.Throws<VipsException>(() => MediaService.Inspect(colour.WriteToBuffer(".tif")));
		}

		// the header tells how big an image would decode before anything is decoded
		[Fact]
		public void The_header_says_how_big_an_image_would_decode()
		{
			using var huge = Image.Black(8000, 6000);
			var header = MediaService.Inspect(huge.WriteToBuffer(".png"));
			Assert.Equal(48_000_000, header.Pixels);
			Assert.False(header.Animated);

			using var frame = (Image.Black(40, 30, bands: 3) + 60).Cast(Enums.BandFormat.Uchar);
			using var frames = Image.Arrayjoin(new[] { frame, frame + 80, frame + 160 }, across: 1).Cast(Enums.BandFormat.Uchar);
			using var paged = frames.Mutate(m => m.Set(GValue.GIntType, "page-height", 30));
			var gif = MediaService.Inspect(paged.WriteToBuffer(".gif"));
			Assert.True(gif.Animated);
			Assert.Equal(3, gif.Pages);
			Assert.Equal(40 * 30 * 3, gif.Pixels);
		}

		[Fact]
		public void Uploaded_images_lose_every_kind_of_metadata()
		{
			var input = JpegWithMetadata(800, 600);
			using (var original = Image.NewFromBuffer(input))
				Assert.Contains("exif-data", original.GetFields());

			var processed = MediaService.ProcessImage(input, 4096, 640);

			using var output = Image.NewFromBuffer(processed.Bytes);
			var fields = output.GetFields();
			Assert.DoesNotContain("exif-data", fields);
			Assert.DoesNotContain("xmp-data", fields);
			Assert.DoesNotContain("iptc-data", fields);
			Assert.DoesNotContain(fields, f => f.StartsWith("exif-ifd"));
			Assert.Equal((800, 600), (processed.Width, processed.Height));
			Assert.Equal("image/jpeg", processed.ContentType);
			using var preview = Image.NewFromBuffer(processed.Preview);
			Assert.Equal(640, Math.Max(preview.Width, preview.Height));
			Assert.DoesNotContain("exif-data", preview.GetFields());
		}

		[Fact]
		public void Large_images_are_capped()
		{
			var processed = MediaService.ProcessImage(JpegWithMetadata(5000, 2500), 4096, 640);

			Assert.Equal((4096, 2048), (processed.Width, processed.Height));
		}

		[Fact]
		public void A_blurhash_is_well_formed()
		{
			var processed = MediaService.ProcessImage(JpegWithMetadata(64, 64), 4096, 640);

			Assert.Equal(28, processed.Blurhash.Length);
			Assert.Equal('L', processed.Blurhash[0]);
		}

		[Fact]
		public void A_white_image_encodes_white_as_its_average()
		{
			var pixels = Enumerable.Range(0, 16 * 16).SelectMany(_ => new byte[] { 255, 255, 255 }).ToArray();

			var hash = Blurhash.Encode(pixels, 16, 16);

			Assert.Equal(28, hash.Length);
			Assert.Equal("TSUA", hash[2..6]);
		}
	}
}