Re^4: Use of uninitialized value $pic

Hello Yes, it wasn't a good night for troubleshooting code. I have incorporated your suggestions and fixed the code.
I used a hash because I have a couple of switches and args that determine which camera is being used and where the files should go.

Moving onto my next problem. I want to call a subroutine ImageNotDark. I want to pass an Image::Magick object ($pic).
By design, the object is not changed inside the subroutine. My problem is that I am not passing the image object correctly.

# Convert to Image::Maggick image
my $pic = Image::Magick->new(magick=>'jpg');  #   create new image obj
+ect
$pic->BlobToImage($img);  #convert the grabbed blob image to Image::Ma
+gick object

## test point A

#pass the $pic object to the subroutine and measure image darkness.
my $test = ImageNotDark ($pic);  #
[download]

The code snippet at the start of the subroutine is as follows:

sub ImageNotDark  {
# Argument is one reference to an image object.
# ImageNotDark compares the image with a blank black canvas.  If the c
+omparison is
# above the defined threshold, the image is bright enough to send (not
+ dark).
# the return value is true if the images is bright enough.

    my $iutImage = Image::Magick->new;  #the image tested for darkness
    $iutImage->Read(@_);  # get the image under test (iut)
[download]

So the debugger shows that $iutImage is not initialised. At test point A, I temporarily added code to save the $pic image to a file.
I was able to confirm that $pic holds a valid image. So I am reasonably certain the problem is the way I call the subroutine and attempt to pass the image. Any tips would be much appreciated.

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Re^5: Use of uninitialized value $pic by haukex (Archbishop) on Apr 25, 2017 at 06:28 UTC
Moving onto my next problem. As this question is unrelated to the rest of the thread, it'd have been better to post it in a new thread. You don't need to construct a new `Image::Magick` over the argument passed to the subroutine. The normal way to handle arguments is (see perlsub): `sub ImageNotDark { my ($iutImage,$arg2,$arg3,...) = @_; # --OR-- my $iutImage = shift; my $arg2 = shift; ...` [download] Or, if your intention were to work with a copy of the image in the subroutine, you could simply do `my $imgCopy = $_[0]->Clone();` inside the subroutine.	[reply] [d/l] [select]
Re^6: Use of uninitialized value $pic by dazz (Beadle) on Apr 25, 2017 at 10:57 UTC
Hello That is diamond advice. My Google search results had not found the perlsub doc and I found conflicting or/and confusing advice around handling objects passed to subs. I am sure this will be helpful to others. I will raise this as a separate question and include your answer for the benefit of others who hit the same problem.	[reply]
Re^5: Use of uninitialized value $pic by zentara (Archbishop) on Apr 25, 2017 at 13:51 UTC
Hi, just a thought. Shouldn't `$iutImage->Read(@_); # get the image under test (iut)` [download] be `my $x = $iutImage->ReadImage($_[0]); warn "$x" if "$x";` [download] Also, you can try passing \$pic to pass the object by reference. I'm not really a human, but I play one on earth. ..... an animated JAPH	[reply] [d/l] [select]
Re^6: Use of uninitialized value $pic by dazz (Beadle) on May 01, 2017 at 10:58 UTC
Hi I don't know. What does this do: `warn "$x" if "$x";` [download] Google tells me it's a warning. Undef?? dazz	[reply] [d/l]
Re^7: Use of uninitialized value $pic by afoken (Chancellor) on May 01, 2017 at 11:03 UTC
It's a very ugly hack for error checking. See "Handling Exceptions" in the documentation of Image::Magick. Sane error handling would use die or the XS equivalent of die inside the Image::Magick code, but now it's too late for an incompatible change. Alexander -- Today I will gladly share my knowledge and experience, for there are no sweeter words than "I told you so". ;-)	[reply]
Re^8: Use of uninitialized value $pic by dazz (Beadle) on May 02, 2017 at 03:36 UTC
Re^9: Use of uninitialized value $pic by afoken (Chancellor) on May 03, 2017 at 06:08 UTC
Re^9: Use of uninitialized value $pic by afoken (Chancellor) on May 02, 2017 at 19:02 UTC
Re^8: Use of uninitialized value $pic by Anonymous Monk on May 01, 2017 at 11:16 UTC


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