[Digikam-users] trouble with image degradation using DK with kipi-plugin: flickr export

[Jean-François Rabasse]

On Sun, 4 Mar 2012, Andrew Goodbody wrote:

> OK, I think we have sorted out what is happening. Both images are marked as 
> being in ProPhotoRGB colour space. But only the one uploaded by 
> FLickrUploader has the embedded ICC profile. The one uploaded by Digikam does 
> not have the embedded profile. I am guessing that the resize for upload is 
> not preserving the embedded profile. Giles, can that be fixed?
>
> Then we have the issue about gwenview etc not using an embedded profile to 
> display an image properly.

Gwenview yes, but also some browsers. Antonio signaled the problem with 
Chrome. Konqueror (used as local image viewer or web browser) doesn't handle 
the profile neither, and shows also the « greenish » version of Jim's image.
For web usage, seems difficult to assume that any user, using any version
of any existing browser, Firefox, Konqueror, Chrome, Safari, Opera, etc.
could see the correct colours.

> So for a workaround, Jim should export any jpegs that he intends to upload 
> with Digikam into the sRGB colour space.

Seems safe.
My own opinion is that colour profiles are rather intended to images
edition software, PhotoShop, GIMP et al., or printing workflows, than
for images display.
Used for images display means the colour information is split into two 
parts, the JPEG scanlines RGB triplets plus the corrective profile data.
If the profile part is lost through an export/upload processing (what 
happened to Jim), or is ignored by the final viewing program (what
happened to those of us using non profiles aware browsers), author's
initial colours are out.

Perhaps a reasonable model for standard web usage could be sRGB default, 
encoded in the Truecolor triplets of the JPEG scanlines.
Nothing extra would be required for final colours rendering.
(Also, uploaded files could be stripped of any non image data.)

However, what could be useful in export/upload modules is at least to
issue a warning, something like « Hey, your image uses an embedded colour
profile and may not be viewed correctly by any user on the earth. Do you
still wish to continue ? »
(Or propose a downsizing+compression+sRGB reencoding process.)

Regards,
Jean-François