bachir
/
popsu-d7


			
				
					
						
						
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  <head>
    <title>
    Aspect Switcher
    </title>
  </head>
  <body>
    <h3>
      Using aspect switcher to create a 'square' setting.
    </h3>
    <p>
      This is done through "chaining" two switches - "is it quite
      wide or not?", then "is it quite tall or not?" which leaves
      us with "must be square then."
    </p>
    <p>
      First we create the three sizes we will be using,
      small-landscape, small-square, small-portrait. I'll just set
      those up with scale_and_crop.
    </p>
    <p>
      We want wide images up to a ratio of 1:0.75 to be rendered
      wide. We want squarish images, with an aspect between 1:0.75
      and 1:1.25 to be rendered square, and anything taller to be
      rendered tall.
    </p>
    <p>
      To do this, we chain 2 rules. We need to build them
      backwards, the smaller sub-rule first, but to understand, I'l
      list them top down.
    </p>
    <p>
      Rule 1. is the master rule, <strong>3-aspects</strong>
    </p>
    <p>
      if ratio is less than 1:.75, use small-landscape. If greater,
      <strong>proceed to rule 2</strong>.
    </p>
    <p>
    </p>
    <p>
      Rule 2. <strong>square-or-portrait</strong>
    </p>
    <p>
      if ratio is less than 1:1.25, use small-square. If greater,
      use small-portrait.
    </p>
    <p>
      To do this, we use the aspect switcher to link to the two
      sizes, and the <em>ratio adjustment</em> to move
      the switching point a little. Set the ratio adjustment to
      1.25
    </p>
    <p>
      With these (5!) rules in place, you can get the desired
      effect. This is a little trickier than just making a 'square'
      setting, but it allows for the required fudge factor to
      handle almost-square images.
    </p>
    <p>
      You can nudge the adjustment factor to be looser or tighter.
      You can create even more chained rules, and define a
      'super-wide' size.
    </p>
    <table border="1" cellpadding="1" cellspacing="1">
      <tbody>
        <tr>
          <td rowspan="1" colspan="1">
            small-landscape  
          </td>
          <td rowspan="1" colspan="1">
            [Scale And Crop]&nbsp;width: 200, height: 100
          </td>
        </tr>
        <tr>
          <td rowspan="1" colspan="1">
            small-portrait
          </td>
          <td rowspan="1" colspan="1">
            [Scale And Crop]&nbsp;width: 100, height: 200
          </td>
        </tr>
        <tr>
          <td rowspan="1" colspan="1">
            small-square
          </td>
          <td rowspan="1" colspan="1">
            [Scale And Crop]&nbsp;width: 140, height: 140
          </td>
        </tr>
        <tr>
          <td rowspan="1" colspan="1">
            small-square-or-portrait
          </td>
          <td rowspan="1" colspan="1">
            [Aspect Switcher] Portrait
            size:&nbsp;<strong>small-portrait</strong>. Landscape
            size:&nbsp;<strong>small-square</strong>&nbsp;(switch
            at 1:1.25)
          </td>
        </tr>
        <tr>
          <td rowspan="1" colspan="1">
            small-3-aspects
          </td>
          <td rowspan="1" colspan="1">
            [Aspect Switcher]&nbsp;Portrait
            size:&nbsp;<strong>small-square-or-portrait</strong>.
            Landscape
            size:&nbsp;<strong>small-landscape</strong>&nbsp;(switch
            at 1:.75)
          </td>
        </tr>
      </tbody>
    </table>
    <p>
      &nbsp;The illustration shows the result of this set-up on a
      collection of images. The listed dimensions are those of the
      source images. You'll see that the mostly-square ones are
      rendered square.
    </p>
    <img src="../docs/aspect-chaining.png" alt="Illustration of several different sized images passing through the above ruleset."/>
    <p>
      The rule being applied is: 1 Is it wide?
    </p>
    <p>
      For image 250x300, the aspect is ( 250/300 = 0.83 ) Normally
      that number (less than 1) would be classified as 'portrait',
      and with the adjustment (*0.75) that is still true, so the
      processing passes through to the portrait preset.
    </p>
    <p>
      rule #2 it it tall?
    </p>
    <p>
      This preset however does a different set of maths, and
      multiplies the aspect by 1.25, producing a result that causes
      it to trigger to 'landscape' choice. 'landscape' at this
      point is set to be the 'square' preset. And we get what we
      wanted.
    </p>
  </body>
</html>