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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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162
163<div class="main">
164
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]165<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>
166
167<h2><a href="http://www.imagemagick.org/api/MagickCore/shear
168_8c.html" target="source" name="AffineTransformImage">AffineTransformImage</a></h2>
169<div class="doc-section">
170
171<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>
172
173<p>The format of the AffineTransformImage method is:</p>
174
175<pre class="code">
176 Image *AffineTransformImage(const Image *image,
177 AffineMatrix *affine_matrix,ExceptionInfo *exception)
178</pre>
179
180<p>A description of each parameter follows:</p></ol>
181
182<h5>image</h5>
183<ol><p>the image.</p></ol>
184
185<h5>affine_matrix</h5>
186<ol><p>the affine matrix.</p></ol>
187
188<h5>exception</h5>
189<ol><p>return any errors or warnings in this structure.</p></ol>
190
191 </div>
192<h2><a href="http://www.imagemagick.org/api/MagickCore/shear
193_8c.html" target="source" name="DeskewImage">DeskewImage</a></h2>
194<div class="doc-section">
195
196<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>
197
198<p>The format of the DeskewImage method is:</p>
199
200<pre class="code">
201 Image *DeskewImage(const Image *image,const double threshold,
202 ExceptionInfo *exception)
203</pre>
204
205<p>A description of each parameter follows:</p></ol>
206
207<h5>image</h5>
208<ol><p>the image.</p></ol>
209
210<h5>threshold</h5>
211<ol><p>separate background from foreground.</p></ol>
212
213<h5>exception</h5>
214<ol><p>return any errors or warnings in this structure.</p></ol>
215
216 </div>
217<h2><a href="http://www.imagemagick.org/api/MagickCore/shear
218_8c.html" target="source" name="RotateImage">RotateImage</a></h2>
219<div class="doc-section">
220
221<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>
222
223<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>
224
225<p>The format of the RotateImage method is:</p>
226
227<pre class="code">
228 Image *RotateImage(const Image *image,const double degrees,
229 ExceptionInfo *exception)
230</pre>
231
232<p>A description of each parameter follows.</p></ol>
233
234<h5>image</h5>
235<ol><p>the image.</p></ol>
236
237<h5>degrees</h5>
238<ol><p>Specifies the number of degrees to rotate the image.</p></ol>
239
240<h5>exception</h5>
241<ol><p>return any errors or warnings in this structure.</p></ol>
242
243 </div>
244<h2><a href="http://www.imagemagick.org/api/MagickCore/shear
245_8c.html" target="source" name="ShearImage">ShearImage</a></h2>
246<div class="doc-section">
247
cristyeaedf062010-05-29 22:36:02 +0000[diff] [blame]248<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]249
250<p>ShearImage() is based on the paper "A Fast Algorithm for General Raster Rotatation" by Alan W. Paeth.</p></ol>
251
252<p>The format of the ShearImage method is:</p>
253
254<pre class="code">
255 Image *ShearImage(const Image *image,const double x_shear,
256 const double y_shear,ExceptionInfo *exception)
257</pre>
258
259<p>A description of each parameter follows.</p></ol>
260
261<h5>image</h5>
262<ol><p>the image.</p></ol>
263
264<h5>x_shear, y_shear</h5>
265<ol><p>Specifies the number of degrees to shear the image.</p></ol>
266
267<h5>exception</h5>
268<ol><p>return any errors or warnings in this structure.</p></ol>
269
270 </div>
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