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- <title>6.5. Scale Image</title>
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- <th colspan="3" align="center" id="chaptername">6. Image</th>
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- <td width="20%" align="left"><a accesskey="p" href="ch05s06s04.html">Prev</a> </td>
- <th width="60%" align="center" id="sectionname">6.5. Scale Image</th>
- <td width="20%" align="right"> <a accesskey="n" href="ch05s06s06.html">Next</a></td>
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- <div class="sect2" lang="en" xml:lang="en">
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- <div>
- <div>
- <h3 class="title"><a id="gimp-image-scale"></a>6.5. Scale Image</h3>
- </div>
- </div>
- </div>
- <a id="id3467725" class="indexterm"></a>
- <div class="mediaobject">
- <img src="../images/dialogs/dialogs-image-scale-image.png" />
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- <div class="simplesect" lang="en" xml:lang="en">
- <div class="titlepage">
- <div>
- <div>
- <h4 class="title"><a id="id3467747"></a>Overview</h4>
- </div>
- </div>
- </div>
- <p>
- The Scale Image function enlarges or reduces the image. It
- changes the scale of the image content and resizes the canvas
- so that the whole image remains visible.
- It also gives you informations about the size and the resolution
- your image will have when printed.
- </p>
- <p>
- It acts on the whole image. If your image has layers with
- different sizes, it is possible that making the image smaller
- will shrink some of them completely away. If this happens you
- will be warned before the operation is applied.
- </p>
- <p>
- If you want to scale a particular layer, use the function Scale
- Layer
- </p>
- </div>
- <div class="simplesect" lang="en" xml:lang="en">
- <div class="titlepage">
- <div>
- <div>
- <h4 class="title"><a id="id3467784"></a>Pixel Dimensions</h4>
- </div>
- </div>
- </div>
- <p>
- You must remember that an image can be located in four places:
- In the image file, in the RAM after loading, on your screen
- when displayed, on paper after printing.
- </p>
- <p>
- This section deals with making your image bigger or smaller,
- what dimensions will be in RAM and then in file after saving.
- </p>
- <p>
- When you open the dialog, the displayed dimensions are that of
- the original image. On screen, all pixels are displayed and the
- dimensions depend on the screen resolution and on the
- <a href="ch05s05s02.html" title="5.2. Dot for Dot">Dot dor Dot</a> option
- you have choosen.
- </p>
- <p>
- You can set there the <span class="emphasis"><em>Width</em></span> and the
- <span class="emphasis"><em>Height</em></span> you want to give to your image by
- adding or removing pixels, resulting in a variation of
- dimensions.
- Click on arrowheads to change the value in the text box. If you
- have clicked in this box, you can use the Up and Down arrow keys
- for precise setting.
- You can act directly on linear dimensions in the unit you want,
- and that will add or remove pixels. These linear
- dimensions in memory are not much useful: they depend on
- resolution and are different from that on screen. Only pixels
- are important, from which the section name.
- </p>
- <p>
- <span class="emphasis"><em>Ratio</em></span> is the ratio between the original
- dimension and the new dimension, for each X and Y axis. Default
- is 1. You can change it. If the adjacent Chain is intact both
- axis will develop jointly. If you break it by clicking on it,
- then you can set every axis separately: this will result in
- deforming the image.
- </p>
- <p>
- You can enlarge an image safely only if the original has a high
- resolution, pixels enough to avoid adding new pixels. Else,
- missing pixels are calculated by interpolation but no new detail
- is added and the more enlarged the more blurred, with aliasing.
- You can improve the result by using the filter
- <a href="ch06s06s06.html" title="6.6. Sharpen">Sharpen</a> (after scaling)
- but the best method is to use a high resolution when scanning an
- image you plan to enlarge.
- </p>
- <p>
- Reducing your image may be necessary if you intend it to a Web
- page. You have to take in account that Internet users still have
- 15' screens and that your big image cann't be completely
- displayed on them. Most of screens work in 800x600 and 1024x768
- resolution.
- </p>
- <p>
- Adding or removing pixels is called "Resampling".
- </p>
- </div>
- <div class="simplesect" lang="en" xml:lang="en">
- <div class="titlepage">
- <div>
- <div>
- <h4 class="title"><a id="id3467901"></a>Print Size & Display Unit</h4>
- </div>
- </div>
- </div>
- <p>
- This section deals with the size and resolution your image will
- have when printed. Remember that all the pixels of the image
- will be printed and that there will be no splitting.
- </p>
- <p>
- When you launch the Scale function GIMP displays the dimensions
- of the original image that will allow printing without
- deformation.
- </p>
- <p>
- As for screen, you can enlarge or reduce the printed image with
- the same risks.
- </p>
- <p>
- Resolution deals with ouput resolution, that is the number of
- pixels that will be used in every inch of the printed image. You
- must not mistake the output resolution with the printer
- resolution which is expressed in dpi (dot per inch): several
- dots are necessary to print a pixel.
- </p>
- <p>
- The resolution proposed by GIMP is the resolution of the
- original image. If you increase the output resolution the
- printed image will be smaller since more pixels are used for an
- inch. Conversely and for the same reason resizing modifies
- resolution.
- </p>
- <p>
- Increasing resolution results in increasing the printed image
- sharpness. This is quite different from simply reducing the
- image size since no pixels are removed.
- </p>
- <p>
- Modifying resolution also acts for the image file. It is not
- visible at the pixel level but it is at the dimension level
- (inch for example). By reducing resolution you decrease the
- dimensions in the image file. By combining resolution reduction
- and pixel reduction and by restablishing the original dimensions
- of your image you can reduce the weight of your image file if
- PNG compression is not enough.
- </p>
- </div>
- <div class="simplesect" lang="en" xml:lang="en">
- <div class="titlepage">
- <div>
- <div>
- <h4 class="title"><a id="id3467975"></a>Interpolation Type</h4>
- </div>
- </div>
- </div>
- <p>
- Here you can select the method used to interpolate the color of
- added pixels, valid for screen display and printing.
- </p>
- <div class="itemizedlist">
- <ul type="disc">
- <li>
- <p>
- <span class="emphasis"><em>None</em></span>: no interpolation is used. Pixels
- are simply enlarged as they are when zooming.
- </p>
- </li>
- <li>
- <p>
- <span class="emphasis"><em>Linear</em></span>:
- </p>
- </li>
- <li>
- <p>
- <span class="emphasis"><em>Cubic</em></span>: The best method but needing much
- calculation.
- </p>
- </li>
- </ul>
- </div>
- <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
- <table border="0" summary="Note">
- <tr>
- <td rowspan="2" align="center" valign="top" width="25">
- <img alt="[Note]" src="../images/note.png" />
- </td>
- <th align="left">Note</th>
- </tr>
- <tr>
- <td colspan="2" align="left" valign="top">
- <p>
- To prepare your image for printing in a particular format use the
- <a href="ch03s04s02.html" title="4.2. Crop Tool">Crop</a> tool, with inch for unit:
- The displayed size is the printing size.
- </p>
- </td>
- </tr>
- </table>
- </div>
- <a id="gimp-image-scale-warning"></a>
- <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
- <table border="0" summary="Note">
- <tr>
- <td rowspan="2" align="center" valign="top" width="25">
- <img alt="[Note]" src="../images/note.png" />
- </td>
- <th align="left">Note</th>
- </tr>
- <tr>
- <td colspan="2" align="left" valign="top">
- <p>
- If scaling would produce an image larger than the "Maximum new
- image size" set in the <a href="ch04s18s14.html" title="18.14. Environment">Environment</a> page of the
- Preferences dialog, you are warned and asked to confirm that you
- really want to do it. Saying yes will not necessarily have bad
- consequences, but you should give it a moment of thought, because
- very large images consume a lot of resources, and outrageously
- large images may consume more resources than you have, causing GIMP
- to crash or otherwise behave unpleasantly.
- </p>
- </td>
- </tr>
- </table>
- </div>
- </div>
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- <td width="40%" align="right" valign="top"> 6.6. Crop Image</td>
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