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76 lines
2.3 KiB
76 lines
2.3 KiB
KDE Image I/O library
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---------------------
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This library allows applications that use the Qt library
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(i.e. QImageIO, TQImage, QPixmap and friends) to read and
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write images in extra formats. Current formats include:
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JPEG <read> <write>
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JPEG2000 <read> <write>
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XV <read> <write>
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EPS <read> <write>
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NETPBM <incomplete>
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PNG <read> <write, only with newer libraries>
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TIFF <read>
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TGA <read> <write>
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PCX <read> <write>
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SGI <read> <write> (images/x-rgb: *.bw, *.rgb, *.rgba, *.sgi)
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DDS <read>
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XCF <read>
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(Some example files are in kdenonbeta/kimgio_examples.)
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To use these formats, you only need to:
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1. link the application with the libtdeio library
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2. Include the <kimageio.h> header
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3. call KImageIO::registerFormats() once, somewhere in your code
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before you load an image.
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Writing handlers
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----------------
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0. Please read the documentation for the QImageIO class in the Qt
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documentation.
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1. When writing handlers, there is a function naming convention;
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suppose, for example, we were writing PNG read and write handlers,
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we would name them
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void kimgio_png_read ( QImageIO * );
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void kimgio_png_write( QImageIO * );
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ie
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kimgio_<format>_<read/write>
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This should reduce the chance of identifier clashes with other code.
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2. Remember that a given KDE application may try to load dozens of
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images at once such as when loading icons, or creating thumbnails.
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Also, it may well be loading them over a network connection.
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Therefore,
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- Avoid creating temporary files or allocating too much memory
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when decoding and encoding. Especially try to avoid firing off
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external programs.
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- Don't assume that the IODevice which is the source or target
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of the image data is pointing to a file on the local filesystem.
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Use the IODevice methods to read and write image data.
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- Check for file corruption or premature end of the image,
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especially before using values read from the file
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e.g. for memory allocations.
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3. If you only have either a reader or the writer for a particular
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format, don't use NULL in QImageIO::defineIOHandler. Instead, write
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a stub function for the unimplemented handler which displays a message
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on standard output. This prevents kimgio-using programs dumping core
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when attempting to call the unimplemented handler.
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Yours in good faith and pedantry,
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Sirtaj Singh Kang <taj@kde.org>, 23 September 1998.
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