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cristyffb69ed2010-12-25 00:06:48 +0000[diff] [blame]11 <title>ImageMagick: MagickCore, C API for ImageMagick: Shear or Rotate an Image by an Arbitrary Angle</title>
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211
212<div class="main">
213
cristy350dea42011-02-15 17:31:04 +0000[diff] [blame]214<h1>Module shear Methods</h1>
cristy6f77f692011-02-15 15:31:39 +0000[diff] [blame]215<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>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]216
cristy350dea42011-02-15 17:31:04 +0000[diff] [blame]217<h2><a href="http://www.imagemagick.org/api/MagickCore/shear_8c.html" id="AffineTransformImage">AffineTransformImage</a></h2>
cristy6f77f692011-02-15 15:31:39 +0000[diff] [blame]218<div class="doc-section">
219
220<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>
221
222<p>The format of the AffineTransformImage method is:</p>
223
224<pre class="code">
225 Image *AffineTransformImage(const Image *image,
226 AffineMatrix *affine_matrix,ExceptionInfo *exception)
227</pre>
228
229<p>A description of each parameter follows:</p>
230
231<h5>image</h5>
232<p>the image.</p>
233
234<h5>affine_matrix</h5>
235<p>the affine matrix.</p>
236
237<h5>exception</h5>
238<p>return any errors or warnings in this structure.</p>
239
240 </div>
cristy350dea42011-02-15 17:31:04 +0000[diff] [blame]241<h2><a href="http://www.imagemagick.org/api/MagickCore/shear_8c.html" id="DeskewImage">DeskewImage</a></h2>
cristy6f77f692011-02-15 15:31:39 +0000[diff] [blame]242<div class="doc-section">
243
244<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>
245
246<p>The format of the DeskewImage method is:</p>
247
248<pre class="code">
249 Image *DeskewImage(const Image *image,const double threshold,
250 ExceptionInfo *exception)
251</pre>
252
253<p>A description of each parameter follows:</p>
254
255<h5>image</h5>
256<p>the image.</p>
257
258<h5>threshold</h5>
259<p>separate background from foreground.</p>
260
261<h5>exception</h5>
262<p>return any errors or warnings in this structure.</p>
263
264 </div>
cristy350dea42011-02-15 17:31:04 +0000[diff] [blame]265<h2><a href="http://www.imagemagick.org/api/MagickCore/shear_8c.html" id="RotateImage">RotateImage</a></h2>
cristy6f77f692011-02-15 15:31:39 +0000[diff] [blame]266<div class="doc-section">
267
268<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>
269
270<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>
271
272<p>The format of the RotateImage method is:</p>
273
274<pre class="code">
275 Image *RotateImage(const Image *image,const double degrees,
276 ExceptionInfo *exception)
277</pre>
278
279<p>A description of each parameter follows.</p>
280
281<h5>image</h5>
282<p>the image.</p>
283
284<h5>degrees</h5>
285<p>Specifies the number of degrees to rotate the image.</p>
286
287<h5>exception</h5>
288<p>return any errors or warnings in this structure.</p>
289
290 </div>
cristy350dea42011-02-15 17:31:04 +0000[diff] [blame]291<h2><a href="http://www.imagemagick.org/api/MagickCore/shear_8c.html" id="ShearImage">ShearImage</a></h2>
cristy6f77f692011-02-15 15:31:39 +0000[diff] [blame]292<div class="doc-section">
293
294<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>
295
296<p>ShearImage() is based on the paper "A Fast Algorithm for General Raster Rotatation" by Alan W. Paeth.</p>
297
298<p>The format of the ShearImage method is:</p>
299
300<pre class="code">
301 Image *ShearImage(const Image *image,const double x_shear,
302 const double y_shear,ExceptionInfo *exception)
303</pre>
304
305<p>A description of each parameter follows.</p>
306
307<h5>image</h5>
308<p>the image.</p>
309
310<h5>x_shear, y_shear</h5>
311<p>Specifies the number of degrees to shear the image.</p>
312
313<h5>exception</h5>
314<p>return any errors or warnings in this structure.</p>
315
316 </div>
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