More Methods

    # Filename: mylibrary.pl
    package Image::Base ; # Switch to this class to build on it.
    
    sub mytransform {
        my $self  = shift ;
        my $class = ref( $self ) || $self ;

        # Perform your transformation here; might be drawing a line or filling
        # a rectangle or whatever... getting/setting pixels using $self->xy().
    }

    package main ; # Switch back to the default package.

Now if you "require" mylibrary.pl after you've "use"d Image::Xpm or any other Image::Base inheriting classes then all these classes will inherit your "mytransform()" method.

new_from_image()

    my $bitmap = Image::Xbm->new( -file => 'bitmap.xbm' ) ;
    my $pixmap = $bitmap->new_from_image( 'Image::Xpm', -cpp => 1 ) ;
    $pixmap->save( 'pixmap.xpm' ) ;

Note that the above will only work if you've installed Image::Xbm and Image::Xpm, but will work correctly for any image object that inherits from Image::Base and respects its API.

You can use this method to transform an image to another image of the same type but with some different characteristics, e.g.

    my $p = Image::Xpm->new( -file => 'test1.xpm' ) ;
    my $q = $p->new_from_image( ref $p, -cpp => 2, -file => 'test2.xpm' ) ;
    $q->save ;

line()

    $i->line( $x0, $y0, $x1, $y1, $colour ) ;

Draw a line from point ($x0,$y0) to point ($x1,$y1) in colour $colour.

                ***                         
           *****                            
       ****                                 
    ***

ellipse()

    $i->ellipse( $x0, $y0, $x1, $y1, $colour ) ;
    $i->ellipse( $x0, $y0, $x1, $y1, $colour, $fill ) ;

Draw an oval enclosed by the rectangle whose top left is ($x0,$y0) and bottom right is ($x1,$y1) using a line colour of $colour. If optional argument $fill is true then the ellipse is filled.

       *********                            
     **         **                          
    *             *                         
     **         **                          
       *********

rectangle()

    $i->rectangle( $x0, $y0, $x1, $y1, $colour ) ;
    $i->rectangle( $x0, $y0, $x1, $y1, $colour, $fill ) ;

Draw a rectangle whose top left is ($x0,$y0) and bottom right is ($x1,$y1) using a line colour of $colour. If $fill is true then the rectangle will be filled.

    ***************                         
    *             *                         
    *             *                         
    *             *                         
    ***************

diamond()

    $i->diamond( $x0, $y0, $x1, $y1, $colour ) ;
    $i->diamond( $x0, $y0, $x1, $y1, $colour, $fill ) ;

Draw a diamond shape within the rectangle top left ($x0,$y0) and bottom right ($x1,$y1) using a $colour. If optional argument $fill is true then the diamond is filled. For example

           ***        
       ****   ****
    ***           ***
       ****   ****
           ***

new()

Recommend that it at least supports "-file" (filename), "-width" and "-height".

new_from_serialised()

serialise()

get()

    my $width = $i->get( -width ) ;
    my( $hotx, $hoty ) = $i->get( -hotx, -hoty ) ;

Get any of the object's attributes. Multiple attributes may be requested in a single call.

See "xy" get/set colours of the image itself.

set()

Set any of the object's attributes. Multiple attributes may be set in a single call; some attributes are read-only.

See "xy" get/set colours of the image itself.

xy()

    $i->xy( 4, 11, '#123454' ) ;    # Set the colour at point 4,11
    my $colour = $i->xy( 9, 17 ) ;  # Get the colour at point 9,17

Get/set colours using x, y coordinates; coordinates start at 0.

When called to set the colour the value returned is class specific; when called to get the colour the value returned is the colour name, e.g. 'blue' or '#f0f0f0', etc, e.g.

    $colour = xy( $x, $y ) ;  # e.g. #123456 
    xy( $x, $y, $colour ) ;   # Return value is class specific

We don't normally pick up the return value when setting the colour.

load()

    $i->load ;
    $i->load( 'test.xpm' ) ;

Load the image from the "-file" attribute filename. Or if a filename parameter is given then set "-file" to that name and load it.

save()

    $i->save ;
    $i->save( 'test.xpm' ) ;

Save the image to the "-file" attribute filename. Or if a filename parameter is given then set "-file" to that name and save to there.

The save format depends on the "Image::Base" subclass. Some implement a "-file_format" attribute if multiple formats can be saved.

add_colours()

    $i->add_colours( $name, $name, ...)

The drawing functions add colours as necessary, so this is just a way to pre-load the palette.

"add_colours()" does nothing for images which don't have a palette or can't take advantage of pre-loading colour names. The base code in "Image::Base" is a no-op.

Lines

Would there be merit in rounding odd numbers of pixels according to which way around line ends are given? Eg. a line 0,0 to 4,1 might do 2 pixels on y=0 and 3 on y=1, but 4,1 to 0,0 the other way around. Or better to have consistency either way around? For reference, in the X11 drawing model the order of the ends doesn't matter for "wide" lines, but for implementation-dependent "thin" lines it's only encouraged, not required.

Ellipses

The current ellipse code ends up with 0.5's in the values, which means floating point, but is still exact since binary fractions like 0.5 are exactly representable. Some rearrangement and factors of 2 could make it all-integer. The "discriminator" in the calculation may exceed 53-bits of float mantissa at around 160,000 pixels wide or high. That might affect the accuracy of the pixels chosen, but should be no worse than that.

Diamond

Image Libraries