Sometimes PNG files cannot be decoded

[inforithmics]

Description

Skia Sharp 2.88.0-preview.232 does not display a png fully - in 2.88.0-preview.209 it works

Code

private void OnPaintSurface(object sender, SKPaintSurfaceEventArgs e)
		{
			// the the canvas and properties
			var canvas = e.Surface.Canvas;

			// make sure the canvas is blank
			canvas.Clear(SKColors.White);

			using var stream = File.Open(@"osm-liberty.png", FileMode.Open, FileAccess.Read, FileShare.Read);
			var data = SKData.Create(stream);
			var image = SKImage.FromEncodedData(data);

			// draw image
			canvas.DrawImage(image, new SKRect(0, 0, image.Width, image.Height));
		}

This should be displayed

But this is displayed

Basic Information

• Version with issue: 2.88.0-preview.232
• Last known good version: 2.88.0-preview.209
• IDE: Visual Studio 2022 17.1.2
• Platform Target Frameworks: .Net Framework 4.8
  • Windows Classic: Windows 11

Reproduction Link

WPF.zip

[inforithmics]

I tried 2.88.0-preview.254 the issue is still there

[ziriax]

I also noticed corruption of PNGs loaded with SkiaSharp 2.88 (in my case these were 16-bit PNGs)

[inforithmics]

I played a bit around (Resaving it with Paint.net, when i Saved it as 8-bit image it worked 24 Bit or 32 Bit showed artefacts)

[inforithmics]

Inspired by this I tried to load the png With Image

#640

does not work:

            var stream = File.Open(@"osm-liberty.png", FileMode.Open, FileAccess.Read, FileShare.Read);
            var data = SKData.Create(stream);
            var image = SKImage.FromEncodedData(data);

            // draw image
            canvas.DrawImage(image, new SKRect(0, 0, image.Width, image.Height));

works:

          var bytes = ImageToByteArray(System.Drawing.Image.FromFile("osm-liberty.png"));
          var image = SKImage.FromEncodedData(bytes);

           // draw image
           canvas.DrawImage(image, new SKRect(0, 0, image.Width, image.Height));

           byte[] ImageToByteArray(System.Drawing.Image image)
           {
               using (var ms = new System.IO.MemoryStream())
               {
                   image.Save(ms, System.Drawing.Imaging.ImageFormat.Png);
                   return ms.ToArray();
               }
           }

So it seems the png File could not be properly decoded.

[inforithmics]

So it seems the Encoding of the Original Image does not work. (The resaved Image is slightly larger 5Kb and has some more Metadata).

[inforithmics]

The workaround won't work on mobile Platforms, because Image is there not available

[inforithmics]

I made some research and libpng is used for decoding png images.

From this issue:

#718

This Version of libpng is used.
https://skia.googlesource.com/third_party/libpng.git@386707c6d19b974ca2e3db7f5c61873813c6fe44

looking at the history some png decoding Bugfixes where made. But I cannot tell if it would work.
https://skia.googlesource.com/third_party/libpng/+log/a37d4836519517bdce6cb9d956092321eca3e73b

[inforithmics]

I checked the png Image with pngcheck and it seems to be valid.

Not working:

File: osm-liberty.png (48207 bytes)
chunk IHDR at offset 0x0000c, length 13
512 x 248 image, 32-bit RGB+alpha, non-interlaced
chunk IDAT at offset 0x00025, length 32768
zlib: deflated, 32K window, default compression
row filters (0 none, 1 sub, 2 up, 3 avg, 4 paeth):
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 (183 out of 248)
chunk IDAT at offset 0x08031, length 15370
row filters (0 none, 1 sub, 2 up, 3 avg, 4 paeth):
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 (248 out of 248)
chunk IEND at offset 0x0bc47, length 0
No errors detected in osm-liberty.png (4 chunks, 90.5% compression).

working:

File: osm-liberty.png (52355 bytes)
chunk IHDR at offset 0x0000c, length 13
512 x 248 image, 32-bit RGB+alpha, non-interlaced
chunk sRGB at offset 0x00025, length 1
rendering intent = perceptual
chunk gAMA at offset 0x00032, length 4: 0.45455
chunk IDAT at offset 0x00042, length 52269
zlib: deflated, 32K window, fast compression
row filters (0 none, 1 sub, 2 up, 3 avg, 4 paeth):
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 (248 out of 248)
chunk IEND at offset 0x0cc7b, length 0
No errors detected in osm-liberty.png (5 chunks, 89.7% compression)

What I see is that the compression method is different so maybe it is a bug in the zlib used for decompressing.

[geckomx]

Same or similar problem when moving from .NET 5 to .NET 6 . ( Nuget packet 2.80.2 and 2.80.3 )

using SKImage:

byte[] rawData = Load();
SKImage img = SKImage.FromEncodedData(rawData);

i get corrupted image

using SKBitmap

SKBitmap bmp = SKBitmap.Decode(rawData);

i get null

With .NET 5 both variants work.

[mattleibow]

Just compiled a debug version of skia and it loads fine. Building release now to see if that is the thing, or maybe my computer is the fix.

If it breaks in release, I'll try step through and see where it goes. I'll also update libpng and see.

Hopefully I can see why it works in some cases. I also wonder if other platforms work, or is everyone broken.