Incorrect XMLDoc of APNG

[Poker-sang]

Prerequisites

• I have written a descriptive issue title
• I have verified that I am running the latest version of ImageSharp
• I have verified if the problem exist in both DEBUG and RELEASE mode
• I have searched open and closed issues to ensure it has not already been reported

ImageSharp version

4.0

Other ImageSharp packages and versions

no

Environment (Operating system, version and so on)

no

.NET Framework version

no

Description

The FrameDelay for APNG should be measured in seconds. XMLdoc incorrectly states it as 1/100th of a second.

No logical errors apart from the documentation.

ImageSharp/src/ImageSharp/Formats/Png/PngFrameMetadata.cs

Lines 33 to 39 in 3948fa8

	/// <summary>
	/// Gets or sets the frame delay for animated images.
	/// If not 0, when utilized in Png animation, this field specifies the number of hundredths (1/100) of a second to
	/// wait before continuing with the processing of the Data Stream.
	/// The clock starts ticking immediately after the graphic is rendered.
	/// </summary>
	public Rational FrameDelay { get; set; } = new(0);

Steps to Reproduce

no

Images

No response

[JimBobSquarePants]

The spec says 1/100 seconds

https://www.w3.org/TR/png/#fcTL-chunk

[Poker-sang]

It said

display the current frame, in seconds

and

If the denominator is 0, it is to be treated as if it were 100 (that is, delay_num then specifies 1/100ths of a second)

[Poker-sang]

If the document is correct, then these are wrong.

ImageSharp/src/ImageSharp/Formats/Png/PngFrameMetadata.cs

Line 66 in 3948fa8

FrameDelay = new Rational(metadata.Duration.TotalMilliseconds / 1000),

ImageSharp/src/ImageSharp/Formats/Png/PngFrameMetadata.cs

Line 83 in 3948fa8

Duration = TimeSpan.FromMilliseconds(delay * 1000),

[JimBobSquarePants]

You’re right, I misread the spec; the XML docs are wrong here. FrameDelay represents a fraction of a second (delay_num / delay_den), not centiseconds. I’ll get the docs fixed. Thanks for flagging it.