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11 <title>ImageMagick: MagickCore, C API for ImageMagick: Shear or Rotate an Image by an Arbitrary Angle</title>
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17 <meta name="Description" content="ImageMagick® is a software suite to create, edit, and compose bitmap images. It can read, convert and write images in a variety of formats (about 100) including GIF, JPEG, JPEG-2000, PNG, PDF, PhotoCD, TIFF, and DPX. Use ImageMagick to translate, flip, mirror, rotate, scale, shear and transform images, adjust image colors, apply various special effects, or draw text, lines, polygons, ellipses and Bézier curves. ImageMagick is free software delivered as a ready-to-run binary distribution or as source code that you can freely use, copy, modify, and distribute. Its license is compatible with the GPL. It runs on all major operating systems. The functionality of ImageMagick is typically utilized from the command line or you can use the features from programs written in your favorite programming language. Choose from these interfaces: MagickCore (C), MagickWand (C), ChMagick (Ch), Magick++ (C++), JMagick (Java), L-Magick (Lisp), PascalMagick (Pascal), PerlMagick (Perl), MagickWand for PHP (PHP), PythonMagick (Python), RMagick (Ruby), or TclMagick (Tcl/TK). With a language interface, use ImageMagick to modify or create images automagically and dynamically."/>
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148<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>
149
150<h2><a href="http://www.imagemagick.org/api/MagickCore/shear
151_8c.html" target="source" name="AffineTransformImage">AffineTransformImage</a></h2>
152<div class="doc-section">
153
154<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>
155
156<p>The format of the AffineTransformImage method is:</p>
157
158<pre class="code">
159 Image *AffineTransformImage(const Image *image,
160 AffineMatrix *affine_matrix,ExceptionInfo *exception)
161</pre>
162
163<p>A description of each parameter follows:</p></ol>
164
165<h5>image</h5>
166<ol><p>the image.</p></ol>
167
168<h5>affine_matrix</h5>
169<ol><p>the affine matrix.</p></ol>
170
171<h5>exception</h5>
172<ol><p>return any errors or warnings in this structure.</p></ol>
173
174 </div>
175<h2><a href="http://www.imagemagick.org/api/MagickCore/shear
176_8c.html" target="source" name="DeskewImage">DeskewImage</a></h2>
177<div class="doc-section">
178
179<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>
180
181<p>The format of the DeskewImage method is:</p>
182
183<pre class="code">
184 Image *DeskewImage(const Image *image,const double threshold,
185 ExceptionInfo *exception)
186</pre>
187
188<p>A description of each parameter follows:</p></ol>
189
190<h5>image</h5>
191<ol><p>the image.</p></ol>
192
193<h5>threshold</h5>
194<ol><p>separate background from foreground.</p></ol>
195
196<h5>exception</h5>
197<ol><p>return any errors or warnings in this structure.</p></ol>
198
199 </div>
200<h2><a href="http://www.imagemagick.org/api/MagickCore/shear
201_8c.html" target="source" name="RotateImage">RotateImage</a></h2>
202<div class="doc-section">
203
204<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>
205
206<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>
207
208<p>The format of the RotateImage method is:</p>
209
210<pre class="code">
211 Image *RotateImage(const Image *image,const double degrees,
212 ExceptionInfo *exception)
213</pre>
214
215<p>A description of each parameter follows.</p></ol>
216
217<h5>image</h5>
218<ol><p>the image.</p></ol>
219
220<h5>degrees</h5>
221<ol><p>Specifies the number of degrees to rotate the image.</p></ol>
222
223<h5>exception</h5>
224<ol><p>return any errors or warnings in this structure.</p></ol>
225
226 </div>
227<h2><a href="http://www.imagemagick.org/api/MagickCore/shear
228_8c.html" target="source" name="ShearImage">ShearImage</a></h2>
229<div class="doc-section">
230
231<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>
232
233<p>ShearImage() is based on the paper "A Fast Algorithm for General Raster Rotatation" by Alan W. Paeth.</p></ol>
234
235<p>The format of the ShearImage method is:</p>
236
237<pre class="code">
238 Image *ShearImage(const Image *image,const double x_shear,
239 const double y_shear,ExceptionInfo *exception)
240</pre>
241
242<p>A description of each parameter follows.</p></ol>
243
244<h5>image</h5>
245<ol><p>the image.</p></ol>
246
247<h5>x_shear, y_shear</h5>
248<ol><p>Specifies the number of degrees to shear the image.</p></ol>
249
250<h5>exception</h5>
251<ol><p>return any errors or warnings in this structure.</p></ol>
252
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