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12 <title>ImageMagick: MagickCore, C API for ImageMagick: Shear or Rotate an Image by an Arbitrary Angle</title>
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145</div>
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147
148</div>
149
150<div class="main">
151
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]152<p class="navigation-index">[<a href="#AffineTransformImage">AffineTransformImage</a> &bull; <a href="#DeskewImage">DeskewImage</a> &bull; <a href="#RotateImage">RotateImage</a> &bull; <a href="#ShearImage">ShearImage</a>]</p>
153
154<h2><a href="http://www.imagemagick.org/api/MagickCore/shear
155_8c.html" target="source" name="AffineTransformImage">AffineTransformImage</a></h2>
156<div class="doc-section">
157
158<p>AffineTransformImage() transforms an image as dictated by the affine matrix. It allocates the memory necessary for the new Image structure and returns a pointer to the new image.</p></ol>
159
160<p>The format of the AffineTransformImage method is:</p>
161
162<pre class="code">
163 Image *AffineTransformImage(const Image *image,
164 AffineMatrix *affine_matrix,ExceptionInfo *exception)
165</pre>
166
167<p>A description of each parameter follows:</p></ol>
168
169<h5>image</h5>
170<ol><p>the image.</p></ol>
171
172<h5>affine_matrix</h5>
173<ol><p>the affine matrix.</p></ol>
174
175<h5>exception</h5>
176<ol><p>return any errors or warnings in this structure.</p></ol>
177
178 </div>
179<h2><a href="http://www.imagemagick.org/api/MagickCore/shear
180_8c.html" target="source" name="DeskewImage">DeskewImage</a></h2>
181<div class="doc-section">
182
183<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></ol>
184
185<p>The format of the DeskewImage method is:</p>
186
187<pre class="code">
188 Image *DeskewImage(const Image *image,const double threshold,
189 ExceptionInfo *exception)
190</pre>
191
192<p>A description of each parameter follows:</p></ol>
193
194<h5>image</h5>
195<ol><p>the image.</p></ol>
196
197<h5>threshold</h5>
198<ol><p>separate background from foreground.</p></ol>
199
200<h5>exception</h5>
201<ol><p>return any errors or warnings in this structure.</p></ol>
202
203 </div>
204<h2><a href="http://www.imagemagick.org/api/MagickCore/shear
205_8c.html" target="source" name="RotateImage">RotateImage</a></h2>
206<div class="doc-section">
207
208<p>RotateImage() 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. RotateImage allocates the memory necessary for the new Image structure and returns a pointer to the new image.</p></ol>
209
210<p>RotateImage() is based on the paper "A Fast Algorithm for General Raster Rotatation" by Alan W. Paeth. RotateImage is adapted from a similar method based on the Paeth paper written by Michael Halle of the Spatial Imaging Group, MIT Media Lab.</p></ol>
211
212<p>The format of the RotateImage method is:</p>
213
214<pre class="code">
215 Image *RotateImage(const Image *image,const double degrees,
216 ExceptionInfo *exception)
217</pre>
218
219<p>A description of each parameter follows.</p></ol>
220
221<h5>image</h5>
222<ol><p>the image.</p></ol>
223
224<h5>degrees</h5>
225<ol><p>Specifies the number of degrees to rotate the image.</p></ol>
226
227<h5>exception</h5>
228<ol><p>return any errors or warnings in this structure.</p></ol>
229
230 </div>
231<h2><a href="http://www.imagemagick.org/api/MagickCore/shear
232_8c.html" target="source" name="ShearImage">ShearImage</a></h2>
233<div class="doc-section">
234
235<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></ol>
236
237<p>ShearImage() is based on the paper "A Fast Algorithm for General Raster Rotatation" by Alan W. Paeth.</p></ol>
238
239<p>The format of the ShearImage method is:</p>
240
241<pre class="code">
242 Image *ShearImage(const Image *image,const double x_shear,
243 const double y_shear,ExceptionInfo *exception)
244</pre>
245
246<p>A description of each parameter follows.</p></ol>
247
248<h5>image</h5>
249<ol><p>the image.</p></ol>
250
251<h5>x_shear, y_shear</h5>
252<ol><p>Specifies the number of degrees to shear the image.</p></ol>
253
254<h5>exception</h5>
255<ol><p>return any errors or warnings in this structure.</p></ol>
256
257 </div>
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