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annotate Doc/lib/libimghdr.tex @ 5817:48b94de85bf3 legacy-trunk

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author Guido van Rossum <guido@python.org>
date Thu, 17 Jul 1997 16:29:42 +0000
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children 3468ea8645ca
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1 \section{Standard module \sectcode{imghdr}}
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2 \stmodindex{imghdr}
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3
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4 The \code{imghdr} module determines the type of image contained in a
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5 file or byte stream.
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6
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7 The \code{imghdr} module defines the following function:
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8
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9 \renewcommand{\indexsubitem}{(in module imghdr)}
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10
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11 \begin{funcdesc}{what}{filename\optional{\, h}}
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12 Tests the image data contained in the file named by \var{filename},
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13 and returns a string describing the image type. If optional \var{h}
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14 is provided, the \var{filename} is ignored and \var{h} is assumed to
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15 contain the byte stream to test.
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16 \end{funcdesc}
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17
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18 The following image types are recognized, as listed below with the
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19 return value from \code{what}:
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20
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21 \begin{enumerate}
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22 \item[``rgb''] SGI ImgLib Files
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23
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24 \item[``gif''] GIF 87a and 89a Files
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25
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26 \item[``pbm''] Portable Bitmap Files
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27
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28 \item[``pgm''] Portable Graymap Files
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29
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30 \item[``ppm''] Portable Pixmap Files
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31
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32 \item[``tiff''] TIFF Files
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33
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34 \item[``rast''] Sun Raster Files
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35
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36 \item[``xbm''] X Bitmap Files
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37
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38 \item[``jpeg''] JPEG data in JIFF format
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39 \end{enumerate}
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40
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41 You can extend the list of file types \code{imghdr} can recognize by
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42 appending to this variable:
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43
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44 \begin{datadesc}{tests}
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45 A list of functions performing the individual tests. Each function
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46 takes two arguments: the byte-stream and an open file-like object.
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47 When \code{what()} is called with a byte-stream, the file-like
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48 object will be \code{None}.
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49
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50 The test function should return a string describing the image type if
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51 the test succeeded, or \code{None} if it failed.
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52 \end{datadesc}
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53
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54 Example:
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55
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56 \begin{verbatim}
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57 >>> import imghdr
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58 >>> imghdr.what('/tmp/bass.gif')
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59 'gif'
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60 \end{verbatim}