Legacy ImageMagick Discussions Archive

Hi,

Under Dos, with IM v7, sometimes I need to identify the Width of the image using convert, then use this variable later in my connvert command, without any pipe.
I'm a little lost on how about to perform this...

Here, I am trying to reduce image Width by its width minus 12 pixels, for example :
(I know my syntax is not the good one, and this code does not work...) PS: My example is only for "example purpose"... What I need is really a way to extract some data about the image thanks to the "Percent Escape Properties", and re-use this information later in my command-line.

Would someone have an idea ? The docs are not very "verbose" about it http://www.imagemagick.org/Usage/basics/#identify_alt
Thank you (and sorry for this newb' question)

You cannot mix pixel width with percent width in the resize arguments. So you would have to use [fx:100*(w-12)/w]x100% or %[fx:w-12]x%[fx:h].

If you want to save a calculation, use -set option:size "%[fx:w-12]x%[fx:h]", then later -resize "%[size] in IM 7

IM 6 does not allow inline calculations to be used later for -resize or most other operators (except for -distort).

If using IM 7, then replace convert with magick (or convert.exe with magic.exe). In IM 6 be sure you are not confusing the Window convert.exe with the Imagemagick convert.exw.

To resize the image so the width reduces by 12 and the height is unchanged, the obvious command, in v7, is: Note that for "-resize WxH", I have not supplied a height, so that isn't changed.

More generally, if you want to save a value for use later in the command, use "-set option", eg:
If using these in Windows BAT scripts, double every %.

Hi Fred, Hi Snibgo,

Thank you very much : Using dynamic variables works perfectly in command-line : I really thank you for this, I was not able to make that work in the past !

However, As I am using the COM+ Object, unsing variables seems not possible using the 'Convert' tool (Even in command-line, dynamic variables only work with the "Magick" tool).
Do you confirm me that there is not way to use variables using "convert" ?

I will try to post that question in the "COM+ Object" forum, even if it is not very busy, sadly.

IM V7 will accept an %[fx:...] expression in most places it expects a number, such as in "-resize".

IM v6 is more restricted. %[fx:...] expressions can only be used in certain places (like "-distort SRT"), but not in "-resize".

Of course, if you are using IM within a programming language, you can evaluate expressions in that language.

Yes Snibgo, I am currently using VBScript to evaluate expressions, but between several IM command-lines.
In some cases, I could gain speed and improve performance by letting IM do simple computing in dynamic variables (such as for exemple dividing a number, or substracting ...)

FYI, the support for the "magick" command in the COM+ Object is planned to be added in the next release of ImageMagick, as I suggested it in this ticket :
https://github.com/ImageMagick/ImageMagick/issues/1083