Create AutoOrient image filter

[jmooring]

This would allow users to fix orientation issues when .Exif.Tags.Orientation is one of 2, 4, 5 or 7.

Ref: https://discourse.gohugo.io/t/image-processing-rotates-images/

[bep]

Yea, that's a good idea. It's Friday night here and I'm a bit tired, but I suspect there may be a way to make this one filter? Could we not just have a images.Orientation filter that respected the EXIF values?

[jmooring]

Misc thoughts...

Is there much of a performance hit for reading the EXIF info every time?

Is there a circumstance where users might want to flip x/y even when .Exif.Tags.Orientation is 0 or 1?

[bep]

Is there much of a performance hit for reading the EXIF info every time?

No (there is a one time cost)

I borrowed this from somewhere:

Is there a circumstance where users might want to flip x/y even when .Exif.Tags.Orientation is 0 or 1?

Maybe, but the use case we're talking about here is to get the image back in normal orientation, so a images.Orientationthat by default took no arguments should be good.

I suspect that images.Flip would also be useful, but slightly hard to use for the use case above.

[jmooring]

I have a working implementation of this as a function...

{{ with resources.Get "Landscape_7.jpg" }}
  {{ with images.AutoOrient . }}
    <img src="{{ .RelPermalink }}" width="{{ .Width }}" height="{{ .Height }}" alt="">
  {{ end }}
{{ end }}

...but have not been able to figure out how to access the EXIF data from a filter.

tpl/images/images.go

// AutoOrient returns the given image, rotating and flipping as needed per the
// EXIF orientation value if present.
func (ns *Namespace) AutoOrient(i images.ImageResource) (images.ImageResource, error) {
	var filters = map[int]gift.Filter{
		2: gift.FlipHorizontal(),
		3: gift.Rotate180(),
		4: gift.FlipVertical(),
		5: gift.Transpose(),
		6: gift.Rotate270(),
		7: gift.Transverse(),
		8: gift.Rotate90(),
	}

	if i.Exif() != nil {
		orientation, ok := i.Exif().Tags["Orientation"].(int)
		if ok && orientation >= 2 && orientation <= 8 {
			return i.Filter(filters[orientation])
		}
	}

	return i, nil
}

Testing example (8 landscape orientations, 8 portrait orientations):

git clone --single-branch -b hugo-github-issue-11717 https://github.com/jmooring/hugo-testing hugo-github-issue-11717
cd hugo-github-issue-11717
hugo server

[bep]

@jmooring re. filter vs method, I think I had the same "head scratcher" when implementing the Process filter, which I implemented using an interface to pass the "filter options" back to where the filters are applied:

https://github.com/gohugoio/hugo/blob/master/resources/images/process.go#L26

You could e.g. create a new interface ala:

type ImageFilterFromOrientationProvider interface {
   AutoOrient(orientation int) gift.Filter
}

And then adjust imageResource.Filter to check for the above interface.

[bep]

I deleted my last comment, that doesn't make sense (we cannot modify the filter), I suggest we do as suggested above, with that we can return nil for "no orientation change".

[github-actions]

This issue has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.