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7 <title>ImageMagick: MagickCore, C API for ImageMagick: Shear or Rotate an Image by an Arbitrary Angle</title/>
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167
168<div class="main">
169
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]170<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>
171
172<h2><a href="http://www.imagemagick.org/api/MagickCore/shear
173_8c.html" target="source" name="AffineTransformImage">AffineTransformImage</a></h2>
174<div class="doc-section">
175
176<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>
177
178<p>The format of the AffineTransformImage method is:</p>
179
180<pre class="code">
181 Image *AffineTransformImage(const Image *image,
182 AffineMatrix *affine_matrix,ExceptionInfo *exception)
183</pre>
184
185<p>A description of each parameter follows:</p></ol>
186
187<h5>image</h5>
188<ol><p>the image.</p></ol>
189
190<h5>affine_matrix</h5>
191<ol><p>the affine matrix.</p></ol>
192
193<h5>exception</h5>
194<ol><p>return any errors or warnings in this structure.</p></ol>
195
196 </div>
197<h2><a href="http://www.imagemagick.org/api/MagickCore/shear
198_8c.html" target="source" name="DeskewImage">DeskewImage</a></h2>
199<div class="doc-section">
200
201<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>
202
203<p>The format of the DeskewImage method is:</p>
204
205<pre class="code">
206 Image *DeskewImage(const Image *image,const double threshold,
207 ExceptionInfo *exception)
208</pre>
209
210<p>A description of each parameter follows:</p></ol>
211
212<h5>image</h5>
213<ol><p>the image.</p></ol>
214
215<h5>threshold</h5>
216<ol><p>separate background from foreground.</p></ol>
217
218<h5>exception</h5>
219<ol><p>return any errors or warnings in this structure.</p></ol>
220
221 </div>
222<h2><a href="http://www.imagemagick.org/api/MagickCore/shear
223_8c.html" target="source" name="RotateImage">RotateImage</a></h2>
224<div class="doc-section">
225
226<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>
227
228<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>
229
230<p>The format of the RotateImage method is:</p>
231
232<pre class="code">
233 Image *RotateImage(const Image *image,const double degrees,
234 ExceptionInfo *exception)
235</pre>
236
237<p>A description of each parameter follows.</p></ol>
238
239<h5>image</h5>
240<ol><p>the image.</p></ol>
241
242<h5>degrees</h5>
243<ol><p>Specifies the number of degrees to rotate the image.</p></ol>
244
245<h5>exception</h5>
246<ol><p>return any errors or warnings in this structure.</p></ol>
247
248 </div>
249<h2><a href="http://www.imagemagick.org/api/MagickCore/shear
250_8c.html" target="source" name="ShearImage">ShearImage</a></h2>
251<div class="doc-section">
252
cristyeaedf062010-05-29 22:36:02 +0000[diff] [blame]253<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]254
255<p>ShearImage() is based on the paper "A Fast Algorithm for General Raster Rotatation" by Alan W. Paeth.</p></ol>
256
257<p>The format of the ShearImage method is:</p>
258
259<pre class="code">
260 Image *ShearImage(const Image *image,const double x_shear,
261 const double y_shear,ExceptionInfo *exception)
262</pre>
263
264<p>A description of each parameter follows.</p></ol>
265
266<h5>image</h5>
267<ol><p>the image.</p></ol>
268
269<h5>x_shear, y_shear</h5>
270<ol><p>Specifies the number of degrees to shear the image.</p></ol>
271
272<h5>exception</h5>
273<ol><p>return any errors or warnings in this structure.</p></ol>
274
275 </div>
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