Texts and Transformations: Difference between revisions

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The same transformation we applied to images in [[Images and Transformations]] can be applied to texts, too.  
==A simple text rotation==
Rotate the text "Hello World" by 30° around its lower left corner. Don't forget to update the board at the end, otherwise the transformations is not applied.
<jsxgraph with="500" height="500" box="box1">
(function(){
    var brd, txt;
   
    brd = JXG.JSXGraph.initBoard('box1', {boundingbox:[-5,5,5,-5], axis:true, showNavigation:true, showCopyright:true});
    txt = brd.create('text',[-2,-1, 'Hello World'], {fontSize:30});
 
    // Rotate text around the lower left corner (-2,-1) by 30 degrees.
    var tRot = brd.create('transform', [30.0*Math.PI/180.0, -2,-1], {type:'rotate'});
    tRot.bindTo(txt);
    brd.update();
})();
</jsxgraph>
===The JavaScript code===
<source lang="javascript">
    var brd, txt;
   
    brd = JXG.JSXGraph.initBoard('box1', {boundingbox:[-5,5,5,-5], axis:true, showNavigation:true, showCopyright:true});
    txt = brd.create('text',[-2,-1, 'Hello World'], {fontSize:30});
 
    // Rotate text around the lower left corner (-2,-1) by 30 degrees.
    var tRot = brd.create('transform', [30.0*Math.PI/180.0, -2,-1], {type:'rotate'});
    tRot.bindTo(txt);
    brd.update();
</source>


There are only a few exceptions:
==A more complex example==
* On Firefox and Webkit browsers the display type of text has to be set to 'internal'.
The same transformations we applied to images in [[Images and Transformations]] can be applied to texts, too.  
* To work correctly on Internet Explorer the size of the text box has to be estimated. So, the result may look a little bit different from
other browsers.


Note: In Mediawiki setting the fontSize property of a JSXGraph text with Firefox does not work. Therefore, the "Hello World" string may be displayed
<jsxgraph with="500" height="500" box="box2">
too small.
<jsxgraph with="500" height="500" box="box1">
(function(){
(function(){
     var brd, txt, p0, p1;
     var brd, txt, p0, p1;
    JXG.Options.text.defaultDisplay = 'internal';
      
      
     brd = JXG.JSXGraph.initBoard('box1', {boundingbox:[-5,5,5,-5], axis:true, showNavigation:true, showCopyright:true});
     brd = JXG.JSXGraph.initBoard('box2', {boundingbox:[-5,5,5,-5], axis:true, showNavigation:true, showCopyright:true});
     p0 = brd.create('point', [0,0], {style:5, name:'offset'});  
     p0 = brd.create('point', [0,0], {style:5, name:'offset'});  
     p1 = brd.create('point', [3,0], {style:5, name:'rotate+scale'});  
     p1 = brd.create('point', [3,0], {style:5, name:'rotate+scale'});  
     txt = brd.create('text',[0,0, 'Hello World'], {fontSize:'200%'});
     txt = brd.create('text',[0,0, 'Hello World'], {fontSize:30});


     var tOff = brd.create('transform', [function(){return p0.X()},function(){return p0.Y()}], {type:'translate'});  
     var tOff = brd.create('transform', [function(){return p0.X()},function(){return p0.Y()}], {type:'translate'});  
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                                         function(){return p1.Dist(p0)/3;}], {type:'scale'});  
                                         function(){return p1.Dist(p0)/3;}], {type:'scale'});  
     tOffInv.bindTo(txt); tScale.bindTo(txt); tOff.bindTo(txt);
     tOffInv.bindTo(txt); tScale.bindTo(txt); tOff.bindTo(txt);
})();
})();
</jsxgraph>
</jsxgraph>
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<source lang="javascript">
<source lang="javascript">
     var brd, txt, p0, p1;
     var brd, txt, p0, p1;
    JXG.Options.text.defaultDisplay = 'internal';
      
      
     brd = JXG.JSXGraph.initBoard('box1', {boundingbox:[-5,5,5,-5], axis:true, showNavigation:true, showCopyright:true});
     brd = JXG.JSXGraph.initBoard('box2', {boundingbox:[-5,5,5,-5], axis:true, showNavigation:true, showCopyright:true});
     p0 = brd.create('point', [0,0], {style:5, name:'offset'});  
     p0 = brd.create('point', [0,0], {style:5, name:'offset'});  
     p1 = brd.create('point', [3,0], {style:5, name:'rotate+scale'});  
     p1 = brd.create('point', [3,0], {style:5, name:'rotate+scale'});  
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[[Category:Examples]]
[[Category:Examples]]
[[Category:Text]]

Latest revision as of 15:55, 9 August 2023

A simple text rotation

Rotate the text "Hello World" by 30° around its lower left corner. Don't forget to update the board at the end, otherwise the transformations is not applied.

The JavaScript code

    var brd, txt;
    
    brd = JXG.JSXGraph.initBoard('box1', {boundingbox:[-5,5,5,-5], axis:true, showNavigation:true, showCopyright:true});
    txt = brd.create('text',[-2,-1, 'Hello World'], {fontSize:30});

    // Rotate text around the lower left corner (-2,-1) by 30 degrees.
    var tRot = brd.create('transform', [30.0*Math.PI/180.0, -2,-1], {type:'rotate'}); 
    tRot.bindTo(txt);
    brd.update();

A more complex example

The same transformations we applied to images in Images and Transformations can be applied to texts, too.

The JavaScript code

Here is the complete code to accomplish this behaviour.

    var brd, txt, p0, p1;
    
    brd = JXG.JSXGraph.initBoard('box2', {boundingbox:[-5,5,5,-5], axis:true, showNavigation:true, showCopyright:true});
    p0 = brd.create('point', [0,0], {style:5, name:'offset'}); 
    p1 = brd.create('point', [3,0], {style:5, name:'rotate+scale'}); 
    txt = brd.create('text',[0,0, 'Hello World'], {fontSize:30});

    var tOff = brd.create('transform', [function(){return p0.X()},function(){return p0.Y()}], {type:'translate'}); 
    tOff.bindTo(txt);
    tOff.bindTo(p1);
    // Rotate text around point "offset" by dragging point "rotate+scale"
    var tRot = brd.create('transform', [function(){return Math.atan2(p1.Y()-p0.Y(),p1.X()-p0.X())}, p0], {type:'rotate'}); 
    tRot.bindTo(txt);
        
    // Scale text by dragging point "rot+scale"
    // We do this by moving the text back to the origin (inverse of transformation tOff),
    // then scale the text (because scaling "starts from (0,0))
    // Finally, we move the text back to point "Offset"
    var tOffInv = brd.create('transform', [function(){return -p0.X()},function(){return -p0.Y()}], {type:'translate'}); 
    var tScale = brd.create('transform', [function(){return p1.Dist(p0)/3;},
                                        function(){return p1.Dist(p0)/3;}], {type:'scale'}); 
    tOffInv.bindTo(txt); tScale.bindTo(txt); tOff.bindTo(txt);