src/tiff/html/man/TIFFRGBAImage.3tiff.html

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   7 <title>TIFFRGBAImage</title>
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  10
  11 <h1 align=center>TIFFRGBAImage</h1>
  12 <a href="#NAME">NAME</a><br>
  13 <a href="#SYNOPSIS">SYNOPSIS</a><br>
  14 <a href="#DESCRIPTION">DESCRIPTION</a><br>
  15 <a href="#ALTERNATE RASTER FORMATS">ALTERNATE RASTER FORMATS</a><br>
  16 <a href="#SIMULTANEOUS RASTER STORE AND DISPLAY">SIMULTANEOUS RASTER STORE AND DISPLAY</a><br>
  17 <a href="#SUPPORTING ADDITIONAL TIFF FORMATS">SUPPORTING ADDITIONAL TIFF FORMATS</a><br>
  18 <a href="#NOTES">NOTES</a><br>
  19 <a href="#RETURN VALUES">RETURN VALUES</a><br>
  20 <a href="#DIAGNOSTICS">DIAGNOSTICS</a><br>
  21 <a href="#SEE ALSO">SEE ALSO</a><br>
  22
  23 <hr>
  24 <a name="NAME"></a>
  25 <h2>NAME</h2>
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  32 <p>TIFFRGBAImageOK, TIFFRGBAImageBegin, TIFFRGBAImageGet,
  33 TIFFRGBAImageEnd &minus; read and decode an image into a
  34 raster</p>
  35 </td>
  36 </table>
  37 <a name="SYNOPSIS"></a>
  38 <h2>SYNOPSIS</h2>
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  45 <p><b>#include &lt;tiffio.h&gt;</b></p>
  46 <!-- INDENTATION -->
  47 <p><b>typedef unsigned char TIFFRGBValue; typedef struct
  48 _TIFFRGBAImage TIFFRGBAImage;</b></p>
  49 <!-- INDENTATION -->
  50 <p><b>int TIFFRGBAImageOK(TIFF *</b><i>tif</i><b>, char</b>
  51 <i>emsg[1024]</i><b>)<br>
  52 int TIFFRGBAImageBegin(TIFFRGBAImage *</b><i>img</i><b>,
  53 TIFF*</b> <i>tif</i><b>, int</b> <i>stopOnError</i><b>,
  54 char</b> <i>emsg[1024]</i><b>)<br>
  55 int TIFFRGBAImageGet(TIFFRGBAImage *</b><i>img</i><b>,
  56 uint32*</b> <i>raster</i><b>, uint32</b> <i>width</i> <b>,
  57 uint32</b> <i>height</i><b>)<br>
  58 void TIFFRGBAImageEnd(TIFFRGBAImage
  59 *</b><i>img</i><b>)</b></p>
  60 </td>
  61 </table>
  62 <a name="DESCRIPTION"></a>
  63 <h2>DESCRIPTION</h2>
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  70 <p>The routines described here provide a high-level
  71 interface through which <small>TIFF</small> images may be
  72 read into memory. Images may be strip- or tile-based and
  73 have a variety of different characteristics: bits/sample,
  74 samples/pixel, photometric, etc. Decoding state is
  75 encapsulated in a <i>TIFFRGBAImage</i> structure making it
  76 possible to capture state for multiple images and quickly
  77 switch between them. The target raster format can be
  78 customized to a particular application&rsquo;s needs by
  79 installing custom routines that manipulate image data
  80 according to application requirements.</p>
  81 <!-- INDENTATION -->
  82 <p>The default usage for these routines is: check if an
  83 image can be processed using <i>TIFFRGBAImageOK</i>,
  84 construct a decoder state block using
  85 <i>TIFFRGBAImageBegin</i>, read and decode an image into a
  86 target raster using <i>TIFFRGBAImageGet</i>, and then
  87 release resources using <i>TIFFRGBAImageEnd</i>.
  88 <i>TIFFRGBAImageGet</i> can be called multiple times to
  89 decode an image using different state parameters. If
  90 multiple images are to be displayed and there is not enough
  91 space for each of the decoded rasters, multiple state blocks
  92 can be managed and then calls can be made to
  93 <i>TIFFRGBAImageGet</i> as needed to display an image.</p>
  94 <!-- INDENTATION -->
  95 <p>The generated raster is assumed to be an array of
  96 <i>width</i> times <i>height</i> 32-bit entries, where
  97 <i>width</i> must be less than or equal to the width of the
  98 image (<i>height</i> may be any non-zero size). If the
  99 raster dimensions are smaller than the image, the image data
 100 is cropped to the raster bounds. If the raster height is
 101 greater than that of the image, then the image data are
 102 placed in the lower part of the raster. (Note that the
 103 raster is assume to be organized such that the pixel at
 104 location (<i>x</i>,<i>y</i>) is
 105 <i>raster</i>[<i>y</i>*<i>width</i>+<i>x</i>]; with the
 106 raster origin in the <b>lower-left</b> hand corner.)</p>
 107 <!-- INDENTATION -->
 108 <p>Raster pixels are 8-bit packed red, green, blue, alpha
 109 samples. The macros <i>TIFFGetR</i>, <i>TIFFGetG</i>,
 110 <i>TIFFGetB</i>, and <i>TIFFGetA</i> should be used to
 111 access individual samples. Images without Associated Alpha
 112 matting information have a constant Alpha of 1.0 (255).</p>
 113 <!-- INDENTATION -->
 114 <p><i>TIFFRGBAImageGet</i> converts non-8-bit images by
 115 scaling sample values. Palette, grayscale, bilevel,
 116 <small>CMYK</small> , and YCbCr images are converted to
 117 <small>RGB</small> transparently. Raster pixels are returned
 118 uncorrected by any colorimetry information present in the
 119 directory.</p>
 120 <!-- INDENTATION -->
 121 <p>The parameter <i>stopOnError</i> specifies how to act if
 122 an error is encountered while reading the image. If
 123 <i>stopOnError</i> is non-zero, then an error will terminate
 124 the operation; otherwise <i>TIFFRGBAImageGet</i> will
 125 continue processing data until all the possible data in the
 126 image have been requested.</p>
 127 </td>
 128 </table>
 129 <a name="ALTERNATE RASTER FORMATS"></a>
 130 <h2>ALTERNATE RASTER FORMATS</h2>
 131 <!-- INDENTATION -->
 132 <table width="100%" border=0 rules="none" frame="void"
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 135 <td width="8%"></td>
 136 <td width="91%">
 137 <p>To use the core support for reading and processing
 138 <small>TIFF</small> images, but write the resulting raster
 139 data in a different format one need only override the
 140 &lsquo;&lsquo;<i>put methods</i>&rsquo;&rsquo; used to store
 141 raster data. These methods are are defined in the
 142 <i>TIFFRGBAImage</i> structure and initially setup by
 143 <i>TIFFRGBAImageBegin</i> to point to routines that pack
 144 raster data in the default <small>ABGR</small> pixel format.
 145 Two different routines are used according to the physical
 146 organization of the image data in the file:
 147 <i>PlanarConfiguration</i>=1 (packed samples), and
 148 <i>PlanarConfiguration</i>=2 (separated samples). Note that
 149 this mechanism can be used to transform the data before
 150 storing it in the raster. For example one can convert data
 151 to colormap indices for display on a colormap display.</p>
 152 </td>
 153 </table>
 154 <a name="SIMULTANEOUS RASTER STORE AND DISPLAY"></a>
 155 <h2>SIMULTANEOUS RASTER STORE AND DISPLAY</h2>
 156 <!-- INDENTATION -->
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 162 <p>It is simple to display an image as it is being read into
 163 memory by overriding the put methods as described above for
 164 supporting alternate raster formats. Simply keep a reference
 165 to the default put methods setup by
 166 <i>TIFFRGBAImageBegin</i> and then invoke them before or
 167 after each display operation. For example, the
 168 <i>tiffgt</i>(1) utility uses the following put method to
 169 update the display as the raster is being filled:</p>
 170 <!-- INDENTATION -->
 171 <pre>static void
 172 putContigAndDraw(TIFFRGBAImage* img, uint32* raster,
 173     uint32 x, uint32 y, uint32 w, uint32 h,
 174     int32 fromskew, int32 toskew,
 175     unsigned char* cp)
 176 {
 177     (*putContig)(img, raster, x, y, w, h, fromskew, toskew, cp);
 178     if (x+w == width) {
 179      w = width;
 180      if (img-&gt;orientation == ORIENTATION_TOPLEFT)
 181          lrectwrite(0, y-(h-1), w-1, y, raster-x-(h-1)*w);
 182      else
 183          lrectwrite(0, y, w-1, y+h-1, raster);
 184     }
 185 }
 186 </pre>
 187 <!-- INDENTATION -->
 188 <p>(the original routine provided by the library is saved in
 189 the variable <i>putContig</i>.)</p>
 190 </td>
 191 </table>
 192 <a name="SUPPORTING ADDITIONAL TIFF FORMATS"></a>
 193 <h2>SUPPORTING ADDITIONAL TIFF FORMATS</h2>
 194 <!-- INDENTATION -->
 195 <table width="100%" border=0 rules="none" frame="void"
 196        cols="2" cellspacing="0" cellpadding="0">
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 198 <td width="8%"></td>
 199 <td width="91%">
 200 <p>The <i>TIFFRGBAImage</i> routines support the most
 201 commonly encountered flavors of <small>TIFF.</small> It is
 202 possible to extend this support by overriding the
 203 &lsquo;&lsquo;<i>get method</i>&rsquo;&rsquo; invoked by
 204 <i>TIFFRGBAImageGet</i> to read <small>TIFF</small> image
 205 data. Details of doing this are a bit involved, it is best
 206 to make a copy of an existing get method and modify it to
 207 suit the needs of an application.</p>
 208 </td>
 209 </table>
 210 <a name="NOTES"></a>
 211 <h2>NOTES</h2>
 212 <!-- INDENTATION -->
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 218 <p>Samples must be either 1, 2, 4, 8, or 16 bits.
 219 Colorimetric samples/pixel must be either 1, 3, or 4 (i.e.
 220 <i>SamplesPerPixel</i> minus <i>ExtraSamples</i>).</p>
 221 <!-- INDENTATION -->
 222 <p>Palette image colormaps that appear to be incorrectly
 223 written as 8-bit values are automatically scaled to
 224 16-bits.</p>
 225 </td>
 226 </table>
 227 <a name="RETURN VALUES"></a>
 228 <h2>RETURN VALUES</h2>
 229 <!-- INDENTATION -->
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 235 <p>All routines return 1 if the operation was successful.
 236 Otherwise, 0 is returned if an error was encountered and
 237 <i>stopOnError</i> is zero.</p>
 238 </td>
 239 </table>
 240 <a name="DIAGNOSTICS"></a>
 241 <h2>DIAGNOSTICS</h2>
 242 <!-- INDENTATION -->
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 248 <p>All error messages are directed to the
 249 <i>TIFFError</i>(3TIFF) routine.</p>
 250 <!-- INDENTATION -->
 251 <p><b>Sorry, can not handle %d-bit pictures</b>. The image
 252 had <i>BitsPerSample</i> other than 1, 2, 4, 8, or 16.</p>
 253 <!-- INDENTATION -->
 254 <p><b>Sorry, can not handle %d-channel images</b>. The image
 255 had <i>SamplesPerPixel</i> other than 1, 3, or 4.</p>
 256 <!-- INDENTATION -->
 257 <p><b>Missing needed &quot;PhotometricInterpretation&quot;
 258 tag</b>. The image did not have a tag that describes how to
 259 display the data.</p>
 260 <!-- INDENTATION -->
 261 <p><b>No &quot;PhotometricInterpretation&quot; tag, assuming
 262 RGB</b>. The image was missing a tag that describes how to
 263 display it, but because it has 3 or 4 samples/pixel, it is
 264 assumed to be <small>RGB.</small></p>
 265 <!-- INDENTATION -->
 266 <p><b>No &quot;PhotometricInterpretation&quot; tag, assuming
 267 min-is-black</b>. The image was missing a tag that describes
 268 how to display it, but because it has 1 sample/pixel, it is
 269 assumed to be a grayscale or bilevel image.</p>
 270 <!-- INDENTATION -->
 271 <p><b>No space for photometric conversion table</b>. There
 272 was insufficient memory for a table used to convert image
 273 samples to 8-bit <small>RGB.</small></p>
 274 <!-- INDENTATION -->
 275 <p><b>Missing required &quot;Colormap&quot; tag</b>. A
 276 Palette image did not have a required <i>Colormap</i>
 277 tag.</p>
 278 <!-- INDENTATION -->
 279 <p><b>No space for tile buffer</b>. There was insufficient
 280 memory to allocate an i/o buffer.</p>
 281 <!-- INDENTATION -->
 282 <p><b>No space for strip buffer</b>. There was insufficient
 283 memory to allocate an i/o buffer.</p>
 284 <!-- INDENTATION -->
 285 <p><b>Can not handle format</b>. The image has a format
 286 (combination of <i>BitsPerSample</i>,
 287 <i>SamplesPerPixel</i>, and
 288 <i>PhotometricInterpretation</i>) that can not be
 289 handled.</p>
 290 <!-- INDENTATION -->
 291 <p><b>No space for B&amp;W mapping table</b>. There was
 292 insufficient memory to allocate a table used to map
 293 grayscale data to <small>RGB.</small></p>
 294 <!-- INDENTATION -->
 295 <p><b>No space for Palette mapping table</b>. There was
 296 insufficient memory to allocate a table used to map data to
 297 8-bit <small>RGB.</small></p>
 298 </td>
 299 </table>
 300 <a name="SEE ALSO"></a>
 301 <h2>SEE ALSO</h2>
 302 <!-- INDENTATION -->
 303 <table width="100%" border=0 rules="none" frame="void"
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 307 <td width="91%">
 308 <p><b>TIFFOpen</b>(3TIFF), <b>TIFFReadRGBAImage</b>(3TIFF),
 309 <b>TIFFReadRGBAImageOriented</b>(3TIFF),
 310 <b>TIFFReadRGBAStrip</b>(3TIFF),
 311 <b>TIFFReadRGBATile</b>(3TIFF), <b>libtiff</b>(3TIFF)</p>
 312 <!-- INDENTATION -->
 313 <p>Libtiff library home page:
 314 <b>http://www.remotesensing.org/libtiff/</b></p>
 315 </td>
 316 </table>
 317 <hr>
 318 </body>
 319 </html>