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Detecting Null Image Field and/or Default Image

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  • Detecting Null Image Field and/or Default Image

    The problem I have is as follows: In a mobile app I am letting the operator use the device's (phone's) camera to capture an image and upload it to the server. The image field is in the detail view of a list control in a UX. Unfortunately, sometimes a user will fill in the associated text fields but, for whatever reason, fail to actually take the picture (this is an HTML5 app, not Phonegap, BTW). I would like to be able to detect the fact that no picture was taken (I am storing the picture as an embedded image in a MySQL LongBlob field). Via debug in a server-side validate event I've looked at the returned value of the empty Image field and it is NOT empty, it contains some data. However, I don't know if, say, copying that data, hardcoding it and using it to detect an "empty" Image field is reliable or wise. I'd simply like to know if there is a documented way to tell if an Image field is empty (or, more precisely, represents "no picture").

    One suggestion I've seen when searching these boards is to use a standard "No picture" JPEG and testing for some key characters. However, I can't figure out how to put a default value in the Image field.

    Any pointers to resources dealing with this issue would be appreciated.

  • #2
    Re: Detecting Null Image Field and/or Default Image

    Inspect your page and see what's in the .src property of your image control after taking an image and when you don't take an image.

    Then you'll know what to test for.


    • #3
      Re: Detecting Null Image Field and/or Default Image

      Thanks, David.

      Yea, well, as I say, I'd much rather have a built-in function that I can rely on (or which gives me "plausible deniability" :) ) but the image field is returned as character type anyway. It appears that an empty image has "iVBOR" as the first five characters, so that's what I'll test for.

      Of course I COULD write out the character version of the image to a file, then test for its size, but I'm NOT doing that (even if it would work, which I somehow doubt). :)
      Last edited by nlk10010; 05-24-2016, 10:26 AM.