Decode animation on the fly with libwebp 1.1

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Dmitry Baryshev

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Jul 22, 2021, 5:25:23 PMJul 22
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Hi! :)

https://developers.google.com/speed/webp/docs/api#advanced_decoding_api demonstrates how to decode a static image on the fly (e.g. coming from a network source) using WebPIAppend/WebPIDecGetRGB.

Is it possible to do the same for animations?

Or, better, is it possible to supply my own data reading function like we can do with libpng (png_set_read_fn) or libtiff (TIFFClientOpen)?

Thanks in advance!

James Zern

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Jul 22, 2021, 9:12:59 PMJul 22
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Hi,

On Thu, Jul 22, 2021 at 2:25 PM Dmitry Baryshev <dmit...@gmail.com> wrote:
Hi! :)

https://developers.google.com/speed/webp/docs/api#advanced_decoding_api demonstrates how to decode a static image on the fly (e.g. coming from a network source) using WebPIAppend/WebPIDecGetRGB.

Is it possible to do the same for animations?

Yes, but not through the WebPAnimDecoder interface. You'd need to use the demuxer (or manually parse the file) and decode the images with WebPIAppend/WebPIUpdate. The demuxer will need to be recreated with new data, however. This is something that we may improve in the future. Chrome is a good example of using the decoder [1], it handles the reconstruction of the animation similar to the WebPAnimDecoder interface.
 

Or, better, is it possible to supply my own data reading function like we can do with libpng (png_set_read_fn) or libtiff (TIFFClientOpen)?

We have writer functions for the encoder, but no reader functions for the decoder.

 

Thanks in advance!

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Dmitry Baryshev

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Jul 23, 2021, 8:59:08 AMJul 23
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> Yes, but not through the WebPAnimDecoder interface. You'd need to use the demuxer (or manually parse the file) and decode the images with WebPIAppend/WebPIUpdate. The demuxer will need to be recreated with new data, however. This is something that we may improve in the future.

Thanks! It would be great to have an I/O abstraction layer like we have in libpng/libtiff/giflib/etc. supported in all libwebp components (decoder, demuxer etc.). The current approach with WebPIAppend doesn't look like an abstraction and introduces issues with using libwebp in abstract imaging libraries.

пятница, 23 июля 2021 г. в 04:12:59 UTC+3, James Zern:
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