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Pan and Zoom View w/Thumbnail
Author: Galego | Website: http://jason.eastendinteractive.com |

Page 8
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Functions at the root level

These functions are the glue that hold it all together. They are called by the magnifying glass and the slider knob. Somebody really smart could abstract these further than I have...if you do, send me an e-mail attached with the updated version! ;-P

Here's my best practices advice...create an 'actions/functions' layer on any MC you create...especially on the _root layer.

Pre-function code

This code runs when the movie loads before the functions get called...it is still very important

// The base_mag_factor is the correlation of the small picture to the big picture...
_root.base_mag_factor = 5;
// The mag_factor will change as scaling occurs
_root.mag_factor = _root.base_mag_factor;
//Stop so that this doesn't reset willy-nilly on us
stop();

The base_mag_factor is the proportion between your thumbnail and the viewer (viewed) object under the mask. _root.mag_factor starts out baselined, but is variable with the zooming.

The Zoom Function

/*
This function scales the magnifying glass and the bigpicture
It also helps to handle the centering effect on the zoom...
Read the comments on how that happens
*/
function scale_mag (zoom_perc,mag_perc) {
 // getting ready for later...to be able to center
 start_width = _root.mag._width;
 start_height = _root.mag._height;
 //scale it all...
 _root.figure._xscale = (zoom_perc);
 _root.figure._yscale = (zoom_perc);
 _root.mag._xscale = (mag_perc);
 _root.mag._yscale = (mag_perc);
 _root.mag_factor = (zoom_perc/100)*(_root.base_mag_factor);
 _root.zoom_ind = zoom_perc; //updates the percentage viewer
 // The other half keeps scaling in sync and centers the scaling
 // Find out the width and height now
 end_width = _root.mag._width;
 end_height = _root.mag._height;
 // Figure the difference in width and height (x and y)
 x_change = start_width - end_width;
 y_change = start_height - end_height;
 //adjust by half the difference
 _root.mag._x = _root.mag._x + x_change/2;
 _root.mag._y = _root.mag._y + y_change/2;
}

You'll notice the reference to the base_mag_factor (which remains constant)...that is why it has to be defined sepaprately from the mag_factor variable (which changes with the zoom).

The Pan Function

/*
Moves the panel inside the viewing window...
It moves opposite the magnifying glass.
This function is also called when scaling occurs
*/
function move_panel () {
 //trace (_root.mag_factor);
 _root.figure._x = 0 -((_root.mag._x-_root.lilfigure._x)*_root.mag_factor);
 _root.figure._y = 0 -((_root.mag._y-_root.lilfigure._y)*_root.mag_factor);
}

Essentially, the large window object (figure) moves opposite the thumbnail (lilfigure) with the magnification factor figured in. You could also do a simple drag on the object...but the idea here is to keep the inside-outside perspective.

Send me your feedback or questions

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» Level Advanced

Added: : 2002-08-20 Rating: 7.95 Votes: 21 Hits: 1841

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Galego (aka Jason White) is an Instructional Designer and a Capoeirista from Grupo CapuraGinga.

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