Incorrect XMLDoc of APNG

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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

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No response

The spec says 1/100 seconds

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

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)

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),

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.

Fix #2988

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Incorrect XMLDoc of APNG #2988

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	/// <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);

Incorrect XMLDoc of APNG #2988

Description

Prerequisites

ImageSharp version

Other ImageSharp packages and versions

Environment (Operating system, version and so on)

.NET Framework version

Description

Steps to Reproduce

Images

Activity

JimBobSquarePants commented on Sep 20, 2025

Poker-sang commented on Sep 20, 2025

Poker-sang commented on Sep 20, 2025

JimBobSquarePants commented on Sep 20, 2025

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