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author Guido van Rossum <guido@python.org>
date Thu, 17 Jul 1997 16:29:42 +0000
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f47bc5554418 mass changes; fix titles; add examples; correct typos; clarifications;
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1 \section{Built-in Module \sectcode{imgfile}}
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2 \bimodindex{imgfile}
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3
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4 The imgfile module allows python programs to access SGI imglib image
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5 files (also known as \file{.rgb} files). The module is far from
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6 complete, but is provided anyway since the functionality that there is
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7 is enough in some cases. Currently, colormap files are not supported.
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8
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9 The module defines the following variables and functions:
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10
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11 \renewcommand{\indexsubitem}{(in module imgfile)}
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12 \begin{excdesc}{error}
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13 This exception is raised on all errors, such as unsupported file type, etc.
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14 \end{excdesc}
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15
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16 \begin{funcdesc}{getsizes}{file}
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17 This function returns a tuple \code{(\var{x}, \var{y}, \var{z})} where
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18 \var{x} and \var{y} are the size of the image in pixels and
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19 \var{z} is the number of
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20 bytes per pixel. Only 3 byte RGB pixels and 1 byte greyscale pixels
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21 are currently supported.
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22 \end{funcdesc}
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23
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24 \begin{funcdesc}{read}{file}
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25 This function reads and decodes the image on the specified file, and
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26 returns it as a python string. The string has either 1 byte greyscale
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27 pixels or 4 byte RGBA pixels. The bottom left pixel is the first in
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28 the string. This format is suitable to pass to \code{gl.lrectwrite},
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29 for instance.
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30 \end{funcdesc}
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31
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32 \begin{funcdesc}{readscaled}{file\, x\, y\, filter\optional{\, blur}}
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33 This function is identical to read but it returns an image that is
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34 scaled to the given \var{x} and \var{y} sizes. If the \var{filter} and
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35 \var{blur} parameters are omitted scaling is done by
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36 simply dropping or duplicating pixels, so the result will be less than
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37 perfect, especially for computer-generated images.
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38
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39 Alternatively, you can specify a filter to use to smoothen the image
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40 after scaling. The filter forms supported are \code{'impulse'},
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41 \code{'box'}, \code{'triangle'}, \code{'quadratic'} and
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42 \code{'gaussian'}. If a filter is specified \var{blur} is an optional
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43 parameter specifying the blurriness of the filter. It defaults to \code{1.0}.
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44
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45 \code{readscaled} makes no
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46 attempt to keep the aspect ratio correct, so that is the users'
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47 responsibility.
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48 \end{funcdesc}
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49
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50 \begin{funcdesc}{ttob}{flag}
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51 This function sets a global flag which defines whether the scan lines
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52 of the image are read or written from bottom to top (flag is zero,
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53 compatible with SGI GL) or from top to bottom(flag is one,
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54 compatible with X). The default is zero.
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55 \end{funcdesc}
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56
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57 \begin{funcdesc}{write}{file\, data\, x\, y\, z}
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58 This function writes the RGB or greyscale data in \var{data} to image
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59 file \var{file}. \var{x} and \var{y} give the size of the image,
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60 \var{z} is 1 for 1 byte greyscale images or 3 for RGB images (which are
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61 stored as 4 byte values of which only the lower three bytes are used).
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62 These are the formats returned by \code{gl.lrectread}.
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63 \end{funcdesc}