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gerrit-public.fairphone.software / platform / external / ImageMagick / de27d7631fa4cbb36c8bde6001d2c522774b3712 / . / www / api / shear.html
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cristy29f2c972015-07-28 13:37:46 +0000[diff] [blame]9 <title>ImageMagick: MagickCore, C API for ImageMagick: Shear or Rotate an Image by an Arbitrary Angle</title>
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Cristy594d2772015-11-15 10:47:42 -0500[diff] [blame]55<p class="text-center"><a href="shear.html#The XShearImage">The XShearImage</a> &#8226; <a href="shear.html#DeskewImage">DeskewImage</a> &#8226; <a href="shear.html#IntegralRotateImage">IntegralRotateImage</a> &#8226; <a href="shear.html#ShearImage">ShearImage</a> &#8226; <a href="shear.html#ShearRotateImage">ShearRotateImage</a></p>
cristyeed6cb62012-01-28 19:38:34 +0000[diff] [blame]56
Cristye93be682015-11-26 09:07:51 -0500[diff] [blame]57<h2><a href="http://www.imagemagick.org/api/MagickCore/shear_8c.html" id="The_XShearImage">The XShearImage</a></h2>
cristycecc9492015-06-09 16:53:50 +0000[diff] [blame]58
59<p>The XShearImage() and YShearImage() methods are based on the paper "A Fast Algorithm for General Raster Rotatation" by Alan W. Paeth, Graphics Interface '86 (Vancouver). ShearRotateImage() is adapted from a similar method based on the Paeth paper written by Michael Halle of the Spatial Imaging Group, MIT Media Lab.</p>
60
Cristye93be682015-11-26 09:07:51 -0500[diff] [blame]61<h2><a href="http://www.imagemagick.org/api/MagickCore/shear_8c.html" id="DeskewImage">DeskewImage</a></h2>
cristycecc9492015-06-09 16:53:50 +0000[diff] [blame]62
63<p>DeskewImage() removes skew from the image. Skew is an artifact that occurs in scanned images because of the camera being misaligned, imperfections in the scanning or surface, or simply because the paper was not placed completely flat when scanned.</p>
64
65<p>The result will be auto-croped if the artifact "deskew:auto-crop" is defined, while the amount the image is to be deskewed, in degrees is also saved as the artifact "deskew:angle".</p>
66
67<p>If the artifact "deskew:auto-crop" is given the image will be automatically cropped of the excess background. The value is the border width of all pixels around the edge that will be used to determine an average border color for the automatic trim.</p>
68
69<p>The format of the DeskewImage method is:</p>
70
71<pre class="text">
72Image *DeskewImage(const Image *image,const double threshold,
73 ExceptionInfo *exception)
74</pre>
75
76<p>A description of each parameter follows:</p>
77
78<dd>
79</dd>
80
81<dd> </dd>
82<dl class="dl-horizontal">
83<dt>image</dt>
84<dd>the image. </dd>
85
86<dd> </dd>
87<dt>threshold</dt>
88<dd>separate background from foreground. </dd>
89
90<dd> </dd>
91<dt>exception</dt>
92<dd>return any errors or warnings in this structure. </dd>
93
94<dd> </dd>
95</dl>
Cristye93be682015-11-26 09:07:51 -0500[diff] [blame]96<h2><a href="http://www.imagemagick.org/api/MagickCore/shear_8c.html" id="IntegralRotateImage">IntegralRotateImage</a></h2>
cristycecc9492015-06-09 16:53:50 +0000[diff] [blame]97
98<p>IntegralRotateImage() rotates the image an integral of 90 degrees. It allocates the memory necessary for the new Image structure and returns a pointer to the rotated image.</p>
99
100<p>The format of the IntegralRotateImage method is:</p>
101
102<pre class="text">
103Image *IntegralRotateImage(const Image *image,size_t rotations,
104 ExceptionInfo *exception)
105</pre>
106
107<p>A description of each parameter follows.</p>
108
109<dt>image</dt>
110<p>the image.</p>
111
112<dt>rotations</dt>
113<p>Specifies the number of 90 degree rotations.</p>
114
Cristye93be682015-11-26 09:07:51 -0500[diff] [blame]115<h2><a href="http://www.imagemagick.org/api/MagickCore/shear_8c.html" id="ShearImage">ShearImage</a></h2>
cristycecc9492015-06-09 16:53:50 +0000[diff] [blame]116
117<p>ShearImage() creates a new image that is a shear_image copy of an existing one. Shearing slides one edge of an image along the X or Y axis, creating a parallelogram. An X direction shear slides an edge along the X axis, while a Y direction shear slides an edge along the Y axis. The amount of the shear is controlled by a shear angle. For X direction shears, x_shear is measured relative to the Y axis, and similarly, for Y direction shears y_shear is measured relative to the X axis. Empty triangles left over from shearing the image are filled with the background color defined by member 'background_color' of the image.. ShearImage() allocates the memory necessary for the new Image structure and returns a pointer to the new image.</p>
118
119<p>ShearImage() is based on the paper "A Fast Algorithm for General Raster Rotatation" by Alan W. Paeth.</p>
120
121<p>The format of the ShearImage method is:</p>
122
123<pre class="text">
124Image *ShearImage(const Image *image,const double x_shear,
125 const double y_shear,ExceptionInfo *exception)
126</pre>
127
128<p>A description of each parameter follows.</p>
129
130<dt>image</dt>
131<p>the image.</p>
132
133<dt>x_shear, y_shear</dt>
134<p>Specifies the number of degrees to shear the image.</p>
135
136<dt>exception</dt>
137<p>return any errors or warnings in this structure.</p>
138
Cristye93be682015-11-26 09:07:51 -0500[diff] [blame]139<h2><a href="http://www.imagemagick.org/api/MagickCore/shear_8c.html" id="ShearRotateImage">ShearRotateImage</a></h2>
cristycecc9492015-06-09 16:53:50 +0000[diff] [blame]140
141<p>ShearRotateImage() creates a new image that is a rotated copy of an existing one. Positive angles rotate counter-clockwise (right-hand rule), while negative angles rotate clockwise. Rotated images are usually larger than the originals and have 'empty' triangular corners. X axis. Empty triangles left over from shearing the image are filled with the background color defined by member 'background_color' of the image. ShearRotateImage allocates the memory necessary for the new Image structure and returns a pointer to the new image.</p>
142
143<p>ShearRotateImage() is based on the paper "A Fast Algorithm for General Raster Rotatation" by Alan W. Paeth. ShearRotateImage is adapted from a similar method based on the Paeth paper written by Michael Halle of the Spatial Imaging Group, MIT Media Lab.</p>
144
145<p>The format of the ShearRotateImage method is:</p>
146
147<pre class="text">
148Image *ShearRotateImage(const Image *image,const double degrees,
149 ExceptionInfo *exception)
150</pre>
151
152<p>A description of each parameter follows.</p>
153
154<dt>image</dt>
155<p>the image.</p>
156
157<dt>degrees</dt>
158<p>Specifies the number of degrees to rotate the image.</p>
159
160<dt>exception</dt>
161<p>return any errors or warnings in this structure.</p>
162
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