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Diffstat (limited to 'Doc/lib/libimageop.tex')
| -rw-r--r-- | Doc/lib/libimageop.tex | 59 |
1 files changed, 29 insertions, 30 deletions
diff --git a/Doc/lib/libimageop.tex b/Doc/lib/libimageop.tex index 836ae76..4e15117 100644 --- a/Doc/lib/libimageop.tex +++ b/Doc/lib/libimageop.tex @@ -1,9 +1,9 @@ -\section{Built-in module \sectcode{imageop}} +\section{Built-in Module \sectcode{imageop}} \bimodindex{imageop} The \code{imageop} module contains some useful operations on images. It operates on images consisting of 8 or 32 bit pixels -stored in Python strings. This is the same format as used +stored in Python strings. This is the same format as used by \code{gl.lrectwrite} and the \code{imgfile} module. The module defines the following variables and functions: @@ -17,49 +17,48 @@ per pixel, etc. \begin{funcdesc}{crop}{image\, psize\, width\, height\, x0\, y0\, x1\, y1} -This function takes the image in \var{image}, which should by +Return the selected part of \var{image}, which should by \var{width} by \var{height} in size and consist of pixels of -\var{psize} bytes, and returns the selected part of that image. \var{x0}, -\var{y0}, \var{x1} and \var{y1} are like the \code{lrectread} -parameters, i.e. the boundary is included in the new image. -The new boundaries need not be inside the picture. Pixels that fall -outside the old image will have their value set to zero. -If \var{x0} is bigger than \var{x1} the new image is mirrored. The -same holds for the y coordinates. +\var{psize} bytes. \var{x0}, \var{y0}, \var{x1} and \var{y1} are like +the \code{lrectread} parameters, i.e.\ the boundary is included in the +new image. The new boundaries need not be inside the picture. Pixels +that fall outside the old image will have their value set to zero. If +\var{x0} is bigger than \var{x1} the new image is mirrored. The same +holds for the y coordinates. \end{funcdesc} \begin{funcdesc}{scale}{image\, psize\, width\, height\, newwidth\, newheight} -This function returns an \var{image} scaled to size \var{newwidth} by -\var{newheight}. No interpolation is done, scaling is done by -simple-minded pixel duplication or removal. Therefore, computer-generated -images or dithered images will not look nice after scaling. +Return \var{image} scaled to size \var{newwidth} by \var{newheight}. +No interpolation is done, scaling is done by simple-minded pixel +duplication or removal. Therefore, computer-generated images or +dithered images will not look nice after scaling. \end{funcdesc} \begin{funcdesc}{tovideo}{image\, psize\, width\, height} -This function runs a vertical low-pass filter over an image. It does -so by computing each destination pixel as the average of two -vertically-aligned source pixels. The main use of this routine is to -forestall excessive flicker if the image is displayed on a video -device that uses interlacing, hence the name. +Run a vertical low-pass filter over an image. It does so by computing +each destination pixel as the average of two vertically-aligned source +pixels. The main use of this routine is to forestall excessive +flicker if the image is displayed on a video device that uses +interlacing, hence the name. \end{funcdesc} \begin{funcdesc}{grey2mono}{image\, width\, height\, threshold} -This function converts a 8-bit deep greyscale image to a 1-bit deep -image by tresholding all the pixels. The resulting image is tightly -packed and is probably only useful as an argument to \code{mono2grey}. +Convert a 8-bit deep greyscale image to a 1-bit deep image by +tresholding all the pixels. The resulting image is tightly packed and +is probably only useful as an argument to \code{mono2grey}. \end{funcdesc} \begin{funcdesc}{dither2mono}{image\, width\, height} -This function also converts an 8-bit greyscale image to a 1-bit -monochrome image but it uses a (simple-minded) dithering algorithm. +Convert an 8-bit greyscale image to a 1-bit monochrome image using a +(simple-minded) dithering algorithm. \end{funcdesc} \begin{funcdesc}{mono2grey}{image\, width\, height\, p0\, p1} -This function converts a 1-bit monochrome image to an 8 bit greyscale -or color image. All pixels that are zero-valued on input get value -\var{p0} on output and all one-value input pixels get value \var{p1} -on output. To convert a monochrome black-and-white image to greyscale -pass the values \code{0} and \code{255} respectively. +Convert a 1-bit monochrome image to an 8 bit greyscale or color image. +All pixels that are zero-valued on input get value \var{p0} on output +and all one-value input pixels get value \var{p1} on output. To +convert a monochrome black-and-white image to greyscale pass the +values \code{0} and \code{255} respectively. \end{funcdesc} \begin{funcdesc}{grey2grey4}{image\, width\, height} @@ -74,7 +73,7 @@ dithering. \begin{funcdesc}{dither2grey2}{image\, width\, height} Convert an 8-bit greyscale image to a 2-bit greyscale image with -dithering. As for \code{dither2mono}, the dithering algorithm is +dithering. As for \code{dither2mono}, the dithering algorithm is currently very simple. \end{funcdesc} |