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1    <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
2        "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
3    <html xmlns="http://www.w3.org/1999/xhtml">
4      <head>
5        <title>
6        Aspect Switcher
7        </title>
8      </head>
9      <body>
10        <h3>
11          Using aspect switcher to create a 'square' setting.
12        </h3>
13        <p>
14          This is done through "chaining" two switches - "is it quite
15          wide or not?", then "is it quite tall or not?" which leaves
16          us with "must be square then."&nbsp;
17        </p>
18        <p>
19          First we create the three sizes we will be using,
20          small-landscape, small-square, small-portrait. I'll just set
21          those up with scale_and_crop.
22        </p>
23        <p>
24          We want wide images up to a ratio of 1:0.75 to be rendered
25          wide. We want squarish images, with an aspect between 1:0.75
26          and 1:1.25 to be rendered square, and anything taller to be
27          rendered tall.
28        </p>
29        <p>
30          To do this, we chain 2 rules. We need to build them
31          backwards, the smaller sub-rule first, but to understand, I'l
32          list them top down.
33        </p>
34        <p>
35          Rule 1. is the master rule, <strong>3-aspects</strong>
36        </p>
37        <p>
38          if ratio is less than 1:.75, use small-wide. If greater,
39          <strong>proceed to rule 2</strong>.
40        </p>
41        <p>
42        </p>
43        <p>
44          Rule 2.&nbsp;<strong>square-or-portrait</strong>
45        </p>
46        <p>
47          if ratio is less than 1:1.25, use small-square. If greater,
48          use small-portrait.
49        </p>
50        <p>
51          To do this, we use the aspect switcher to link to the two
52          sizes, and the&nbsp;<em>ratio adjustment</em>&nbsp;to move
53          the switching point a little. Set the ratio adjustment to
54          1.25
55        </p>
56        <p>
57          With these (5!) rules in place, you can get the desired
58          effect. This is a little trickier than just making a 'square'
59          setting, but it allows for the required fudge factor to
60          handle almost-square images.
61        </p>
62        <p>
63          You can nudge the adjustment factor to be looser or tighter.
64          You can create even more chained rules, and define a
65          'super-wide' size.
66        </p>
67        <table border="1" cellpadding="1" cellspacing="1">
68          <tbody>
69            <tr>
70              <td rowspan="1" colspan="1">
71                small-landscape
72              </td>
73              <td rowspan="1" colspan="1">
74                [Scale And Crop]&nbsp;width: 200, height: 100
75              </td>
76            </tr>
77            <tr>
78              <td rowspan="1" colspan="1">
79                small-portrait
80              </td>
81              <td rowspan="1" colspan="1">
82                [Scale And Crop]&nbsp;width: 100, height: 200
83              </td>
84            </tr>
85            <tr>
86              <td rowspan="1" colspan="1">
87                small-square
88              </td>
89              <td rowspan="1" colspan="1">
90                [Scale And Crop]&nbsp;width: 140, height: 140
91              </td>
92            </tr>
93            <tr>
94              <td rowspan="1" colspan="1">
95                small-square-or-portrait
96              </td>
97              <td rowspan="1" colspan="1">
98                [Aspect Switcher] Portrait
99                size:&nbsp;<strong>small-portrait</strong>. Landscape
100                size:&nbsp;<strong>small-square</strong>&nbsp;(switch
101                at 1:1.25)
102              </td>
103            </tr>
104            <tr>
105              <td rowspan="1" colspan="1">
106                small-3-aspects
107              </td>
108              <td rowspan="1" colspan="1">
109                [Aspect Switcher]&nbsp;Portrait
110                size:&nbsp;<strong>small-square-or-portrait</strong>.
111                Landscape
112                size:&nbsp;<strong>small-landscape</strong>&nbsp;(switch
113                at 1:.75)
114              </td>
115            </tr>
116          </tbody>
117        </table>
118        <p>
119          &nbsp;The illustration shows the result of this set-up on a
120          collection of images. The listed dimensions are those of the
121          source images. You'll see that the mostly-square ones are
122          rendered square.
123        </p>
124        <img src="../docs/aspect-chaining.png" alt="Illustration of several different sized images passing through the above ruleset."/>
125        <p>
126          The rule being applied is: 1 Is it wide?
127        </p>
128        <p>
129          For image 250x300, the aspect is ( 250/300 = 0.83 ) Normally
130          that number (less than 1) would be classified as 'portrait',
131          and with the adjustment (*0.75) that is still true, so the
132          processing passes through to the portrait preset.
133        </p>
134        <p>
135          rule #2 it it tall?
136        </p>
137        <p>
138          This preset however does a different set of maths, and
139          multiplies the aspect by 1.25, producing a result that causes
140          it to trigger to 'landscape' choice. 'landscape' at this
141          point is set to be the 'square' preset. And we get what we
142          wanted.&nbsp;&nbsp;
143        </p>
144      </body>
145    </html>
146    
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