perltutorial boo_radley This is the second demonstration program I've written for [http://wxperl.sourceforge.net|wxperl]. Jouke mentioned that my last tutorial was better suited to someone familiar with wxperl than not, and I've tried to keep the same level of detail & explanation here.<br/> This script shows how to load and display a file (in this case, a jpeg) into a bitmap control. I found that wxWindows' documentation was unclear on how image handlers interacted with image controls and bitmap controls, and it took a little under two hours to come up with the 9 (!) lines of code to complete the task. It also shows how to implement constraints to keep resized objects looking good.<br/> You'll have to change the name of the file being loaded, but otherwise the script should load as-is.<br/> <readmore> <code>#!/usr/bin/perl use Wx; package MyApp; #As always, we need to subclass Wx::App and populate it with a frame. use strict; use vars qw(@ISA); @ISA=qw(Wx::App); sub OnInit { my $this = @_; my $frame = MyFrame->new( "Mini-image demo", [-1,-1], [-1,-1]); # if the frame didn't get created, exit early. don't use die here, as it seems to be a little unstable... # if OnInit returns false,though, wx will clean up after itself nicely. unless ($frame) {print "unable to create frame -- exiting."; return undef} $frame->Show( 1 ); 1; #everything's ok, on with the show. } package MyFrame; # subclass wx::Frame to insert the image control. use vars qw(@ISA); use strict; # # All we load here are 2 constants used # to keep the image stretched to the dimensions of the window. # use Wx qw( wxWidth wxHeight); # # Wx::Image loads the Image control and all of the Image handlers. # use Wx::Image; use IO::File; @ISA=qw(Wx::Frame); sub new { my $class = shift; my $this = $class->SUPER::new( undef, -1, $_[0], $_[1], $_[2] ); # # replace the filename with something appropriate. # my $file = IO::File->new( "c:/halo2.jpg", "r" ) or return undef; binmode $file; # # define a handler for jpeg images. # handlers are half of what translates file formats (.jpg in this case) # into streams readable by wxBitmap objects for diplay. # yes, this means you typically can't cram a file's contents into # a wxBitmap control -- the exception being windows bitmaps. # # There is a method called 'Wx::Image::FindHandlerType', but I couldn't # get the thing to work in any way, shape or form. # my $handler = Wx::JPEGHandler->new(); # # wxImages are the other half of getting images displayed -- # they hold the data stream created by a handler. # Although there's many functions that can be performed with an wxImage, # all we're interested is turning the stream into a bitmap. # my $image = Wx::Image->new(); my $bmp; # used to hold the bitmap. # # here we load the file into $image. simple enough. # $handler->LoadFile( $image, $file ); # # and here, we turn the data in $image into a bitmap, and store in $bmp. # if the data in $bmp is bad for some reason, $bmp->Ok() will fail. $bmp = $image->ConvertToBitmap(); if( $bmp->Ok() ) { # create a static bitmap called ImageViewer that displays the # selected image. $this->{ImageViewer}= Wx::StaticBitmap->new($this, -1, $bmp); } # At this point, we could just return the frame, and be ok. # unfortunately, the static bitmap could be *really* static and not # resize itself when the window's resized, which'd look pretty ugly. # # To make sure everything looks ok, we'll assign constraints to # Imageviewer. # Layout constraints determine how controls will appear within the # window. They consist of 4 members : left, top, width and height. # constraints are objects by themselves, and need to be assigned to # objects in order to have any use. We'll be using this contstraint # in order to stretch the picture out to the full size of the window. # my $b1 = Wx::LayoutConstraints->new(); # set the upper left corner to absolute [0,0]. # if there were other controls using constraints, we could change these to # something like $b1->left->RightOf ($widget, 5) to make this control appear # 5 pixels to the right of $widget's constraints. $b1->left->Absolute(0); $b1->top->Absolute(0); # now set the width and height to 100% each way. $b1->width->PercentOf( $this, wxWidth,100); $b1->height->PercentOf( $this, wxHeight, 100); # # Now that all the dimensions of the constraint are complete, # assign it to ImageViewer. # $this->{ImageViewer}->SetConstraints( $b1 ); $this; # return the frame object to the calling application. } package main; my $app = MyApp->new();# create an instance of the Wx::App-derived class $app->MainLoop(); # run </code>