Index out of range error

[markolbert]

I'm running into a problem reading a PSD file preparatory to displaying it in a WinUI3 app. Here's the code:

        foreach( var path in paths )
        {
            using var fs = File.Open( path, FileMode.Open, FileAccess.Read, FileShare.Read );

            var psdFile = PsdFile.Open( fs );
            // this next line throws the exception
            var image = psdFile.ImageData.ToImageSharpImage();
            
            var ms = new MemoryStream();
            image.SaveAsJpeg( ms );
            ms.Position = 0;

            var bitmap = new BitmapImage();
            bitmap.SetSource( ms.AsRandomAccessStream() );

            images.Add( bitmap );

The exception is "Index is outside the bounds of the array." It's being thrown from within System.Private.CoreLib.

Thoughts on what might be causing this, or which package I should clone and dig into to get more details?

[markolbert]

I forked PsdSharp and did some spelunking. In C:\Programming\cloned\PsdSharp\PsdSharp\Images\DataConversion\RgbInterleaver.cs a situation is encountered where a request is made for the channel element at the length of the channel array, which causes the out of range exception.

Note that I had to "unparallelize" the Parallel.For construct to see which line was throwing the exception.

    public static byte[] ToInterleavedBuffer(ImageData imageData, ColorType desiredColorType)
    {
        var channelsArray = imageData.GetChannels().ToArray();
        var channels = new Dictionary<Channel, byte[]>()
        {
            { Channel.Red, channelsArray[0].GetData() },
            { Channel.Green, channelsArray[1].GetData() },
            { Channel.Blue, channelsArray[2].GetData() },
        };
        if (channelsArray.Length > 3)
        {
            channels.Add(Channel.Alpha, channelsArray[3].GetData());
        }

        var sourceBytesPerPixel = imageData.ChannelDepth / 8;
        
        //
        // the image I'm processing has 11,899,536 pixels
        //
        var pixelCount = (int)(imageData.Width * imageData.Height);
        var destBytesPerPixel = (int)Math.Ceiling(desiredColorType.Channels.Sum(x => x.PixelCount) / 8d);
        var interleavedBuffer = new byte[pixelCount * destBytesPerPixel];
        var destinationChannels = desiredColorType.Channels;

        var chunkSize = 50_000;
        
        for( var chunk = 0; chunk < ( pixelCount + chunkSize - 1 ) / chunkSize; chunk++ )
        {
            var start = chunk * chunkSize;
            var end = Math.Min(start + chunkSize, pixelCount);

            for (var i = start; i < end; i++)
            {
                var srcOffset = i * sourceBytesPerPixel;
                var destOffset = i * destBytesPerPixel;

                if( srcOffset >= 11316303 )
                    System.Diagnostics.Debugger.Break();

                for (var j = 0; j < destinationChannels.Length; j++)
                {
                    if (!channels.ContainsKey(destinationChannels[j].Channel))
                    {
                        interleavedBuffer[destOffset + j] = 255;
                        continue;
                    }

                    //
                    // when the index i gets to 11,316,303 the out of range exception is thrown.
                    // the first destination channel is only 11,316,303 entries long. But the index of the
                    // requested value is the same, which causes the index out of range exception

                    var channel = channels[destinationChannels[j].Channel];

                    interleavedBuffer[destOffset + j] = sourceBytesPerPixel switch
                    {
                         // the line where the exception is thrown
                        1 => channel[srcOffset],
                        2 => (byte)(BinaryPrimitives.ReadUInt16BigEndian(channel.AsSpan(srcOffset, 2)) >> 8),
#if NET6_0_OR_GREATER
                        _ => (byte)(Math.Clamp(BinaryPrimitives.ReadSingleBigEndian(channel.AsSpan(srcOffset, 4)), 0,
                                               1) * 255)
#else
                        _ => (byte)(Compat.MathCompat.Clamp(Compat.BinaryPrimitivesCompat.ReadSingleBigEndian(channel.AsSpan(srcOffset, 4)), 0, 1) * 255)
#endif
                    };
                }
            }
        }

Hope this helps. I can send you the image that blows up if that would be helpful.

[kaelon141]

Sorry for the late response, I've just spent a month traveling around Europe.
I will look into this soon to push a fix. Thanks for the report!

if you still have the image, please do share it - that would be helpful for debugging.

[markolbert]

Sounds like a fun trip! Unfortunately, I've moved well past this week and no longer remember what caused it. Sorry!