[Mapserver-users] Re: html-type legends with perl mapscript

[Puneet Kishor]

Thanks Sean, Daniel, for responding. However...

> On Monday, May 26, 2003, at 11:00  PM, pkishor_98 wrote:
>
>> ..
>> so, to those who know... please, what is the difference between 
>> createLegendIcon and
>> drawLegendIcon?
>>
>> I want to draw a separate legend icon for each layer, but if a layer 
>> has a more than
>> one classes, I would like to be able to draw a single image file with 
>> icons for all the
>> classes...

On Tuesday, May 27, 2003, at 08:43  AM, Sean Gillies wrote:

> createLegendIcon makes an imageObj of the proper format and size.
> drawLegendIcon draws colors/shapes into the imageObj (passed in
> as the 5th argument).

On Tuesday, May 27, 2003, at 08:41  AM, Daniel Morissette wrote:

> CreateLegendIcon() creates a brand new image with the icon drawn on it.
>
> DrawLegendIcon() draws the legend icon at the specified location in an
> already existing image.

Ok, that is what I figured out late last night, but couldn't validate 
that because I reached no success with my shenanigans. createLeg does 
its job fine, but drawLeg creates a badly formed image... the image is 
formed but can't be opened by either my browser (which hangs) or 
Photoshop which croaks "badly formed file" or some such.

I am not sure how I am going to implement this eventually, but for now 
I want to try out a separate legend icon for each layer. If a layer has 
more than one classes then I want a single image with all the key boxes 
for each class stacked one below another. So, this is what I tried in 
my read-write perl ;-) --

#======
for (0..$mapObj->{numlayers} - 1) {

	# grab the layer
	my $layerObj = $mapObj->getLayer($_);

	# name this layer's legend image
	my $layer_legimg = 'leg_'.$layerObj->{name}.'.png';

	# create a new image object for this layer's legend
	# as wide as the keysize width, and
	# as high as the sum of the heights of all the keys in this layer
	# plus the vertical spacing between the keys
	my $imgObj = new mapscript::imageObj(
                                           $mapObj->{legend}->{keysizex},
                                           (
                                             (
                                               $layerObj->{numclasses} *
                                               
($mapObj->{legend}->{keysizey} + $mapObj->{legend}->{keyspacingy})
                                             ) -
                                             
$mapObj->{legend}->{keyspacingy}
                                           )
                                        );
	# loop over each class
	for (0..$layerObj->{numclasses} - 1) {

		# grab the class
		my $classObj = $layerObj->getClass($_);

		# calculate the vertical offset for this keybox
		my $y_offset = ($_ * ($mapObj->{legend}->{keysizey} + 
$mapObj->{legend}->{keyspacingy}));

		# draw the keybox in the image
          $classObj->drawLegendIcon(
                                     $mapObj,
                                     $layerObj,
                                     $mapObj->{legend}->{keysizex},
                                     $mapObj->{legend}->{keysizey},
                                     $imgObj,
                                     0,
                                     $y_offset
                                   );
	} # end class loop

	# save the image
	$imgObj->saveImage(
                         $imgdir.$layer_legimg,
                         $mapscript::MS_PNG,
                         $mapObj->{interlace},
                         $mapObj->{transparent},
                         $mapObj->{imagequality}
                        );
} # end layer loop

#======

As I said above... I get an image, but it is no good. Is there anything 
wrong in my logic?


>
> Maybe use Perl-GD or ImageMagick to copy and paste individual
> class legendIcons into one image per layer?
>

that is definitely an option, but I'd rather not, since I am accessing 
gd anyway via Mapserver. And drawLegendIcon is supposed to do exactly 
that... the fewer modules I have to depend on, the more portable my 
application.

Many thanks,

Puneet.