Re^2: Pixel setting oddity

Aren't you getting any warnings for that? I'm surprised Image::Magick doesn't complain about the invalid input.

The posted code has a bare string eval without any error checks ($@), so most errors will be silent. Also, Image::Magick requires a lot of manual error checks because it does not use perl's exception mechanism (i.e. die), but instead requires checking return values (as in C). This is documented in http://www.imagemagick.org/script/perl-magick.php#exceptions. The posted code lacks those checks, too.

Alexander

--
Today I will gladly share my knowledge and experience, for there are no sweeter words than "I told you so". ;-)

Comment on Re^2: Pixel setting oddity - Image:Magick

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Re^3: Pixel setting oddity - Image:Magick by Eily (Monsignor) on May 11, 2015 at 12:42 UTC
Thanks for the info on exception handling with Image::Magick! And yes, merrymonk fails to check $@ after the eval, but there wouldn't have been a warning there since this actually works (as in this case the variables are actually in a double quote context). And on the topic of safety and error checking, it does look like the code is not run under strict and warnings ; which would have done nothing for this particular case, but are still very helpful safety nets.	[reply]
Re^4: Pixel setting oddity - Image:Magick by merrymonk (Hermit) on May 12, 2015 at 06:58 UTC
Thank you for that explanation. Indeed is was the single quotes that were stopping it working. When I changed these to 4 double quotes all was well!	[reply]
Re^5: Pixel setting oddity - Image:Magick by afoken (Chancellor) on May 12, 2015 at 08:28 UTC
Indeed is was the single quotes that were stopping it working. When I changed these to 4 double quotes all was well! It may work, but it still hides most, if not all errors, because you don't check $@ after eval and you don't check the return values from Image::Magick. Alexander -- Today I will gladly share my knowledge and experience, for there are no sweeter words than "I told you so". ;-)	[reply]