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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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164
165<div class="main">
166
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]167<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>
168
169<h2><a href="http://www.imagemagick.org/api/MagickCore/shear
170_8c.html" target="source" name="AffineTransformImage">AffineTransformImage</a></h2>
171<div class="doc-section">
172
173<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>
174
175<p>The format of the AffineTransformImage method is:</p>
176
177<pre class="code">
178 Image *AffineTransformImage(const Image *image,
179 AffineMatrix *affine_matrix,ExceptionInfo *exception)
180</pre>
181
182<p>A description of each parameter follows:</p></ol>
183
184<h5>image</h5>
185<ol><p>the image.</p></ol>
186
187<h5>affine_matrix</h5>
188<ol><p>the affine matrix.</p></ol>
189
190<h5>exception</h5>
191<ol><p>return any errors or warnings in this structure.</p></ol>
192
193 </div>
194<h2><a href="http://www.imagemagick.org/api/MagickCore/shear
195_8c.html" target="source" name="DeskewImage">DeskewImage</a></h2>
196<div class="doc-section">
197
198<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>
199
200<p>The format of the DeskewImage method is:</p>
201
202<pre class="code">
203 Image *DeskewImage(const Image *image,const double threshold,
204 ExceptionInfo *exception)
205</pre>
206
207<p>A description of each parameter follows:</p></ol>
208
209<h5>image</h5>
210<ol><p>the image.</p></ol>
211
212<h5>threshold</h5>
213<ol><p>separate background from foreground.</p></ol>
214
215<h5>exception</h5>
216<ol><p>return any errors or warnings in this structure.</p></ol>
217
218 </div>
219<h2><a href="http://www.imagemagick.org/api/MagickCore/shear
220_8c.html" target="source" name="RotateImage">RotateImage</a></h2>
221<div class="doc-section">
222
223<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>
224
225<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>
226
227<p>The format of the RotateImage method is:</p>
228
229<pre class="code">
230 Image *RotateImage(const Image *image,const double degrees,
231 ExceptionInfo *exception)
232</pre>
233
234<p>A description of each parameter follows.</p></ol>
235
236<h5>image</h5>
237<ol><p>the image.</p></ol>
238
239<h5>degrees</h5>
240<ol><p>Specifies the number of degrees to rotate the image.</p></ol>
241
242<h5>exception</h5>
243<ol><p>return any errors or warnings in this structure.</p></ol>
244
245 </div>
246<h2><a href="http://www.imagemagick.org/api/MagickCore/shear
247_8c.html" target="source" name="ShearImage">ShearImage</a></h2>
248<div class="doc-section">
249
cristyeaedf062010-05-29 22:36:02 +0000[diff] [blame]250<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>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]251
252<p>ShearImage() is based on the paper "A Fast Algorithm for General Raster Rotatation" by Alan W. Paeth.</p></ol>
253
254<p>The format of the ShearImage method is:</p>
255
256<pre class="code">
257 Image *ShearImage(const Image *image,const double x_shear,
258 const double y_shear,ExceptionInfo *exception)
259</pre>
260
261<p>A description of each parameter follows.</p></ol>
262
263<h5>image</h5>
264<ol><p>the image.</p></ol>
265
266<h5>x_shear, y_shear</h5>
267<ol><p>Specifies the number of degrees to shear the image.</p></ol>
268
269<h5>exception</h5>
270<ol><p>return any errors or warnings in this structure.</p></ol>
271
272 </div>
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