Aliases .. some thoughts

[Archive]

[Originally posted by themonk on 2007-05-31 15:14:17-07]

Hi Phil...

Any thoughts on the best way of doing this...

This is not a request, just an insight into how people maybe using exiftool.

Aliases are useful for returning a group of values.....

However, another use of them is to check several equivalent locations for metadata.

You maybe looking for one value but it may be defined in several places...

Using the aliases you can define an order of precedence...

e.g Look in EXIF, then in XMP, then in PhotoShop for Resolution.

A problem is that the locations returned by aliases "may" not use any common string which enables us to associate

the value returned with the specified alias. As such we have to call exiftool several times, once for each alias, filter the results,

ignoring everything but the first returned value.

If we had a command line which used three aliases to return three possible values we will get a list of assorted locations/values returned

which then need to be parsed. We need to know what locations map to which aliases in the ExifTool_config to parse these values.

Only then can we match the values returned with the aliases....

There are two possible enhancements here...

1. Use aliases to return a single value from a list of possible locations

2. Be able to use multiple aliases in a single invocation and identify the values returned without
knowing the contents of ExifTool_config

Hope this makes some sort of sense....

[Archive]

[Originally posted by exiftool on 2007-05-31 18:38:26-07]

Hi Mark,

I think I understand at least some of what you are suggesting:

Code:

1. Use aliases to return a single value from a list of possible locations

This is in fact a common purpose of the Composite tags.  So adding a
user-defined Composite tag can give you exactly this functionality.

Code:

2. Be able to use multiple aliases in a single invocation and identify
the values returned without knowing the contents of ExifTool_config

I assume you mean from the command line (since doing this via the API is
easy.)  One way to do this is with something like this (using the -common
and -canon aliases for example):

Code:

> exiftool -common -xxx -canon -f image.jpg
ALIAS1: -
FileName: a.jpg
FileSize: 384 kB
Model: Caplio 500SE
DateTimeOriginal: 2007:05:23 14:30:09
ImageSize: 1280x960
Quality: -
FocalLength: 5.8mm
ShutterSpeed: 1/36
Aperture: 2.5
ISO: 248
WhiteBalance: Auto
Flash: Off
ALIAS2: -
FileName: a.jpg
Model: Caplio 500SE
DateTimeOriginal: 2007:05:23 14:30:09
ShootingMode: -
ShutterSpeed: 1/36
Aperture: 2.5
MeteringMode: Multi-segment
ExposureCompensation: 0
ISO: 248
Lens: -
FocalLength: 5.8mm
ImageSize: 1280x960
Quality: -
FlashOn: -
FlashType: -
ConditionalFEC: -
RedEyeReduction: -
ShutterCurtainHack: -
WhiteBalance: Auto
FocusMode: -
Contrast: -
Sharpness: Normal
Saturation: High
ColorTone: -
FileSize: 384 kB
FileNumber: -
DriveMode: -
OwnerName: -
SerialNumber: -

Here you can see which tags belong to which aliases because I have
asked for the non-existent ALIAS1 and ALIAS2 tags.  With the -f option,
all requested tags are returned, and missing values are indicated by "-".

Does this do what you wanted?

- Phil

[Archive]

[Originally posted by exiftool on 2007-05-31 18:42:33-07]

Oops, sorry.  For the last example I changed my command line but
it got left out when I cut and re-pasted.  Here is the correct command:

Code:

exiftool -ALIAS1 -common -ALIAS2 -canon -f -S a.jpg

- Phil

[Archive]

[Originally posted by themonk on 2007-06-01 10:43:04-07]

Phil

Wow .... Composite Tags combined with 'Desire' or 'Require' !!!!!

This is the perfect solution to everything

1. I can create a composite tag using 'Desire' which looks in all the required locations

   I can then use ValueConv to return the first one that is defined

   As such, only one value is returned........

2. The name that is returned by Composite Tags is the name of the Composite Tag and not the name
   of the 'Desire' tags so I now can combine composite tags in one command call and parse

   the results easily.

This is fantastic stuff..

Mark