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Release 1.0 (Developed under OS 2.2 / OS 3.0) Copyright 1992 by Georges CHAN.
JpegDecode
INHERITS FROM Object
DECLARED IN JpegDecode.h
CLASS DESCRIPTION
JpegDecode is an abstract class for reading a JPEG² (JFIF) file. By incorporating the JpegDecode class to an application, it will enable such application to read a JPEG² file without requiring any prior conversion of the input JPEG² file.The image decoded from the JPEG² file are stored into either an array of NXBitmapImageRep or an array of NXImage.
METHOD TYPES
Initializing a new JpegDecode instance
- initFromFile:
INSTANCE METHODS
initFromFile:
- initFromFile:(const char *) filename
bitMap: (id *) bMap
size: (NXSize *) bitMapSize
mustSee: (BOOL) flag
Initializes the receiver, a NXBitmapImageRep (i.e. bMap), with the image specified in filename, which can be a full or relative pathname. The file should be a JPEG² (JFIF) file of version 1.01 or below. The size of the image is returned through bitMapSize.
The YCbCr color space is the standard color space for JPEG² (JFIF) color images. Such images need to be converted, i.e. from the YCbCr color space to the standard RGB screen color space. If a fatal error occurred during the decoding of such an image, user can tell whether or not the decoder should do the RGB conversion for the partial image obtained so far. The mustSee flag is used for that purpose. If the user wants to convert to RGB (i.e. desperately need to see the non-bogus picture part) then the mustSee flag must be set to YES, otherwise it must be set to NO. Note that, if the mustSee flag is set to YES then there maybe some wrong information displayed in the last row. Furthermore, by setting the mustSee flag to NO, no RGB conversion is performed, i.e. no extra processing time is used.
After finishing the initialization, this method returns self. However, if the new instance can't be initialized or an error occurred during the decoding process, and nil is returned.
- initFromFile:(const char *)filename
image: (id *) im
size: (NXSize *) ImageSize
mustSee: (BOOL) flag
Does the same thing as the previous initFromFile method except that the receiver is a NXImage (i.e. im).
Note: Due to copyright reasons, JPEG² file which uses arithmetic encoding is not processed.
Furthermore, due to the lack of JPEG² sample file which uses CMYK or YIQ color space, thus
no test have been fully done for such files.
² JPEG = Joint Photographic Expert Group
JFIF = JPEG File Interchange Format
These are the contents of the former NiCE NeXT User Group NeXTSTEP/OpenStep software archive, currently hosted by Netfuture.ch.