Support » Plugin: EntryWizard » Check colour space

  • Plugin Contributor teskeyn

    (@teskeyn)


    Would it be possible to add extra checks to upload images in addition to max height, width etc. Ideally check any of the common EXIF fields but in particular I would like to check that the colour space for the uploaded image is sRGB.

Viewing 8 replies - 1 through 8 (of 8 total)
  • Plugin Author Josie Stauffer

    (@joanne123)

    I’d love to do that, but so far I’ve not been able to figure out how to get the information from the .jpg file reliably.

    If someone can tell me how to get the color space in a way that will work for images produced by any camera and any software, I’ll certainly try.

    You’re right that getting the colour space ‘reliably’ is a problem. There are at least three places in a jpg file where colour space information can be stored either as a tag value or as parameter sets or as a profile. It is not possible to assume that all these places agree.
    Then there is the issue of image files without any colour space where sRGB may be assumed but the exact behaviour can differ.
    In terms of managing an event entry, it is probably simpler to get the images regardless and have a checking method outside EntryWizard. Personally I open the downloaded images folder in Adobe Bridge, with appropriate metadata display options.

    Plugin Contributor teskeyn

    (@teskeyn)

    I’ve done some tests with the standard php function exif_read_data, looking at the [ColorSpace] tag which should be set to 1 for sRGB and otherwise undefined. I’ve checked this with images from Canon, Casio, iPhone, Nikon, Olympus, Samsung and Sony which all return a value 1, and Lightroom says they are all sRGB. I also used Lightroom to convert some of these to Adobe RGB and exif_read_data returned a value 65535 for [ColorSpace]. So could this be used for an initial beta test?

    • This reply was modified 1 year, 5 months ago by teskeyn.
    • This reply was modified 1 year, 5 months ago by teskeyn.
    Plugin Author Josie Stauffer

    (@joanne123)

    For my own images from a Panasonic camera, I find that although the jpg files contain the Color Space, the raw ones do not. And it’s the raw files I would start from for competitions.

    Being a maverick in such things, I also use Gimp to edit my images, and it does not add any [ColorSpace] tag to the exif data.

    I might look into adding a test for the exif [ColorSpace], with an option to throw up a warning if the value was not 1. But it would be a bit complicated to code and I’m really short of time at the moment, so no promises, I’m afraid.

    It sounds as if you are a coder — would you be interested in helping?

    Plugin Contributor teskeyn

    (@teskeyn)

    I’d be willing to give it a try – can you contact me off-forum at webmaster@sxpf.org.uk.

    My initial thought was first to modify the text that is displayed on the webform when you upload an image to show the colour space alongside the image height & width. Then add an option in layout to to change the dialog in that display to say something along the lines of “The colour space of this image is not set to sRGB, confirm keep or delete”

    Hi I was also wondering if this was possible? Would be useful to have even if its just info showing that the colour space was/wasnt sRGB.

    Long ago, when digital image projection started seriously, it was stated by most events that sRGB is required. Time has moved on. Most competition software can now handle colour management either in advance (eg, DiCentra) or on the fly during projection.
    sRGB is effectively no longer mandatory, although most events still say they require it. For the events I run, I typically get 5% errors (non-sRGB), but I have had some clubs in an interclub event with up to 80% errors. I track the stats because I am interested, but the practical effects on projection are nil.

    Hi,
    Well, we now have this check in the latest update thanks to Josie.
    The check is on the EXIF data. The EXIF field for colour space only has two defined values – sRGB and Undefined.
    Undefined in EXIF may be divisible into eg, No profile, AdobeRGB, ProPhotoRGB or some other bespoke profile, but that requires looking outside EXIF at other segments in the JPEG file.

Viewing 8 replies - 1 through 8 (of 8 total)
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