why PingImageBlob is so slow when the pic is an animated webp

[justinfx]

There isn't enough information here to offer you any help. You can see how small of a wrapper function PingImageBlob is: https://github.com/gographics/imagick/blob/v3.2.0/imagick/magick_wand_image.go#L1704

So that leads me to believe that the slow performance would have to come from the webp delegate. And you may need to ask about this on the ImageMagick support forum.

[justinfx]

Here is my initial guess...

PingBlob(), which is the underlying call that is made through C.MagickPingImageBlob(), has a check to see if the particular image format supports blobs: https://github.com/ImageMagick/ImageMagick/blob/main/MagickCore/blob.c#L3669

GetMagickSupportBlob looks for a specific flag to be defined by the coder (plugin) for that format: https://github.com/ImageMagick/ImageMagick/blob/0def2d22ca04a68677ae88f275511098752d0ca0/MagickCore/magick.c#L383

The webp coder does not seem to set this flag: https://github.com/ImageMagick/ImageMagick/blob/main/coders/webp.c#L679

So this makes PingBlob() take a different code path and do a full read of the image, write it to a temp file, and then acquire the attributes from that: https://github.com/ImageMagick/ImageMagick/blob/main/MagickCore/blob.c#L3687

If my guess is true, then it would mean webp does not support the fast path because it is a stream-only format and costs as much as reading in the media in the first place.

[hqlzzu]

So this makes PingBlob() take a different code path and do a full read of the image, write it to a temp file

I agree with this point