[BUG] SKPixmap.GetPixelSpan() returns incorrectly sized ReadOnlySpan<byte>

Description

When using SKPixmap to get the raw pixel data via GetPixelSpan(), the length that is used to create the span is incorrectly calculated when a pixmap is derived from ExtractSubset on another pixmap/bitmap (or manually created with a larger-than-normal row size).

Code

// A sample PNG image that is larger than the subset required below (25x25).
// This sample image is sized: 111x33
byte[] imageData = [
    0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A, 0x00, 0x00, 0x00, 0x0D,
    0x49, 0x48, 0x44, 0x52, 0x00, 0x00, 0x00, 0x6F, 0x00, 0x00, 0x00, 0x21,
    0x08, 0x02, 0x00, 0x00, 0x00, 0x58, 0xF5, 0x62, 0x2B, 0x00, 0x00, 0x00,
    0x03, 0x73, 0x42, 0x49, 0x54, 0x08, 0x08, 0x08, 0xDB, 0xE1, 0x4F, 0xE0,
    0x00, 0x00, 0x00, 0x7B, 0x49, 0x44, 0x41, 0x54, 0x68, 0x81, 0xED, 0xDA,
    0xB1, 0x0D, 0x02, 0x51, 0x0C, 0x05, 0xC1, 0x6F, 0x44, 0xFF, 0x2D, 0x9B,
    0x80, 0x13, 0x0D, 0xB0, 0xD2, 0x09, 0x34, 0x13, 0x39, 0xB4, 0x36, 0x7E,
    0xB3, 0xBB, 0x87, 0x8A, 0x9A, 0x95, 0xDD, 0x7D, 0x7E, 0xAE, 0x7B, 0x5F,
    0xF9, 0x75, 0x33, 0x73, 0xCE, 0x79, 0xDC, 0xFD, 0xC6, 0x5F, 0x51, 0xB3,
    0xA4, 0x66, 0x49, 0xCD, 0x92, 0x9A, 0x25, 0x35, 0x4B, 0x6A, 0x96, 0xD4,
    0x2C, 0xA9, 0x59, 0x52, 0xB3, 0xA4, 0x66, 0x49, 0xCD, 0x92, 0x9A, 0x25,
    0x35, 0x4B, 0x6A, 0x96, 0xD4, 0x2C, 0xA9, 0x59, 0x52, 0xB3, 0xA4, 0x66,
    0x49, 0xCD, 0x92, 0x9A, 0x25, 0x35, 0x4B, 0x6A, 0x96, 0xD4, 0x2C, 0xA9,
    0x59, 0x52, 0xB3, 0xA4, 0x66, 0x49, 0xCD, 0xD2, 0xB5, 0xEA, 0x7A, 0x8F,
    0x92, 0xF8, 0xD2, 0x58, 0xC7, 0x85, 0x5E, 0x3B, 0x1C, 0x0F, 0x3A, 0x22,
    0x47, 0x3D, 0x10, 0x00, 0x00, 0x00, 0x00, 0x49, 0x45, 0x4E, 0x44, 0xAE,
    0x42, 0x60, 0x82
];

using var bitmap = SKBitmap.Decode(imageData);

// Get a smaller portion of the bitmap (bottom-right corner--to exemplify the last row requiring less than the
// pixmap's full row bytes).
using var bitmapSubset = new SKBitmap();
if (!bitmap.ExtractSubset(bitmapSubset, SKRectI.Create(bitmap.Width - 25, bitmap.Height - 25, 25, 25)))
    throw new InvalidOperationException("Unable to create subset!");

// Get the subset bitmap's pixmap.
var pixmap = bitmapSubset.PeekPixels();
var pixmapInfo = pixmap.Info;
var pixmapBytes = pixmap.GetPixelSpan();

// Calculate the actual byte length of the pixmap data.
var pixmapActualByteLength = pixmapInfo.Height > 0
    ? ((pixmap.RowBytes * (pixmapInfo.Height - 1)) + pixmapInfo.RowBytes)
    : 0;

// Validate pixmap span's length.
if (pixmapBytes.Length < pixmapActualByteLength)
    throw new InvalidOperationException("Pixel data not fully specified!");

Expected Behavior

No exception should be thrown and SKPixmap.GetPixelSpan() should return a span with a length of 11200 bytes (in this particular example).

The span's length should match the native Skia API: SkPixmap::computeByteSize() which in turn calls SkImageInfo::computeByteSize(pixmap->rowBytes()). Neither of these APIs appear to be available in the exposed/referenced C library. Though it is easy to calculate as seen in the example code above.

Actual Behavior

InvalidOperationException is thrown with the message: Pixel data not fully specified!

Version of SkiaSharp

Other (Please indicate in the description)

Last Known Good Version of SkiaSharp

Other (Please indicate in the description)

IDE / Editor

Visual Studio (Windows)

Platform / Operating System

Windows

Platform / Operating System Version

Tested on Windows 10.0.19045.0 x64, .NET 8.0.1 x64, SkiaSharp 2.88.7.

Devices

In theory, bug should occur on all devices.

Relevant Screenshots

No response

Relevant Log Output

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Code of Conduct

[X] I agree to follow this project's Code of Conduct

mono / SkiaSharp