gwenview/lib/libjpeg/transupp.h

   1 /*
   2  * transupp.h
   3  *
   4  * Copyright (C) 1997, Thomas G. Lane.
   5  * This file is part of the Independent JPEG Group's software.
   6  * For conditions of distribution and use, see the accompanying README file.
   7  *
   8  * This file contains declarations for image transformation routines and
   9  * other utility code used by the jpegtran sample application.  These are
  10  * NOT part of the core JPEG library.  But we keep these routines separate
  11  * from jpegtran.c to ease the task of maintaining jpegtran-like programs
  12  * that have other user interfaces.
  13  *
  14  * NOTE: all the routines declared here have very specific requirements
  15  * about when they are to be executed during the reading and writing of the
  16  * source and destination files.  See the comments in transupp.c, or see
  17  * jpegtran.c for an example of correct usage.
  18  */
  19
  20 #ifndef TRANSUPP_H
  21 #define TRANSUPP_H
  22
  23 /* If you happen not to want the image transform support, disable it here */
  24 #ifndef TRANSFORMS_SUPPORTED
  25 #define TRANSFORMS_SUPPORTED 1          /* 0 disables transform code */
  26 #endif
  27
  28 /* Short forms of external names for systems with brain-damaged linkers. */
  29
  30 #ifdef NEED_SHORT_EXTERNAL_NAMES
  31 #define jtransform_request_workspace            jTrRequest
  32 #define jtransform_adjust_parameters            jTrAdjust
  33 #define jtransform_execute_transformation       jTrExec
  34 #define jcopy_markers_setup                     jCMrkSetup
  35 #define jcopy_markers_execute                   jCMrkExec
  36 #endif /* NEED_SHORT_EXTERNAL_NAMES */
  37
  38
  39 /*
  40  * Codes for supported types of image transformations.
  41  */
  42
  43 typedef enum {
  44         JXFORM_NONE,            /* no transformation */
  45         JXFORM_FLIP_H,          /* horizontal flip */
  46         JXFORM_FLIP_V,          /* vertical flip */
  47         JXFORM_TRANSPOSE,       /* transpose across UL-to-LR axis */
  48         JXFORM_TRANSVERSE,      /* transpose across UR-to-LL axis */
  49         JXFORM_ROT_90,          /* 90-degree clockwise rotation */
  50         JXFORM_ROT_180,         /* 180-degree rotation */
  51         JXFORM_ROT_270          /* 270-degree clockwise (or 90 ccw) */
  52 } JXFORM_CODE;
  53
  54 /*
  55  * Although rotating and flipping data expressed as DCT coefficients is not
  56  * hard, there is an asymmetry in the JPEG format specification for images
  57  * whose dimensions aren't multiples of the iMCU size.  The right and bottom
  58  * image edges are padded out to the next iMCU boundary with junk data; but
  59  * no padding is possible at the top and left edges.  If we were to flip
  60  * the whole image including the pad data, then pad garbage would become
  61  * visible at the top and/or left, and real pixels would disappear into the
  62  * pad margins --- perhaps permanently, since encoders & decoders may not
  63  * bother to preserve DCT blocks that appear to be completely outside the
  64  * nominal image area.  So, we have to exclude any partial iMCUs from the
  65  * basic transformation.
  66  *
  67  * Transpose is the only transformation that can handle partial iMCUs at the
  68  * right and bottom edges completely cleanly.  flip_h can flip partial iMCUs
  69  * at the bottom, but leaves any partial iMCUs at the right edge untouched.
  70  * Similarly flip_v leaves any partial iMCUs at the bottom edge untouched.
  71  * The other transforms are defined as combinations of these basic transforms
  72  * and process edge blocks in a way that preserves the equivalence.
  73  *
  74  * The "trim" option causes untransformable partial iMCUs to be dropped;
  75  * this is not strictly lossless, but it usually gives the best-looking
  76  * result for odd-size images.  Note that when this option is active,
  77  * the expected mathematical equivalences between the transforms may not hold.
  78  * (For example, -rot 270 -trim trims only the bottom edge, but -rot 90 -trim
  79  * followed by -rot 180 -trim trims both edges.)
  80  *
  81  * We also offer a "force to grayscale" option, which simply discards the
  82  * chrominance channels of a YCbCr image.  This is lossless in the sense that
  83  * the luminance channel is preserved exactly.  It's not the same kind of
  84  * thing as the rotate/flip transformations, but it's convenient to handle it
  85  * as part of this package, mainly because the transformation routines have to
  86  * be aware of the option to know how many components to work on.
  87  */
  88
  89 typedef struct {
  90   /* Options: set by caller */
  91   JXFORM_CODE transform;        /* image transform operator */
  92   boolean trim;                 /* if TRUE, trim partial MCUs as needed */
  93   boolean force_grayscale;      /* if TRUE, convert color image to grayscale */
  94
  95   /* Internal workspace: caller should not touch these */
  96   int num_components;           /* # of components in workspace */
  97   jvirt_barray_ptr * workspace_coef_arrays; /* workspace for transformations */
  98 } jpeg_transform_info;
  99
 100
 101 #if TRANSFORMS_SUPPORTED
 102
 103 /* Request any required workspace */
 104 EXTERN(void) jtransform_request_workspace
 105         JPP((j_decompress_ptr srcinfo, jpeg_transform_info *info));
 106 /* Adjust output image parameters */
 107 EXTERN(jvirt_barray_ptr *) jtransform_adjust_parameters
 108         JPP((j_decompress_ptr srcinfo, j_compress_ptr dstinfo,
 109              jvirt_barray_ptr *src_coef_arrays,
 110              jpeg_transform_info *info));
 111 /* Execute the actual transformation, if any */
 112 EXTERN(void) jtransform_execute_transformation
 113         JPP((j_decompress_ptr srcinfo, j_compress_ptr dstinfo,
 114              jvirt_barray_ptr *src_coef_arrays,
 115              jpeg_transform_info *info));
 116
 117 #endif /* TRANSFORMS_SUPPORTED */
 118
 119
 120 /*
 121  * Support for copying optional markers from source to destination file.
 122  */
 123
 124 typedef enum {
 125         JCOPYOPT_NONE,          /* copy no optional markers */
 126         JCOPYOPT_COMMENTS,      /* copy only comment (COM) markers */
 127         JCOPYOPT_ALL            /* copy all optional markers */
 128 } JCOPY_OPTION;
 129
 130 #define JCOPYOPT_DEFAULT  JCOPYOPT_COMMENTS     /* recommended default */
 131
 132 /* Setup decompression object to save desired markers in memory */
 133 EXTERN(void) jcopy_markers_setup
 134         JPP((j_decompress_ptr srcinfo, JCOPY_OPTION option));
 135 /* Copy markers saved in the given source object to the destination object */
 136 EXTERN(void) jcopy_markers_execute
 137         JPP((j_decompress_ptr srcinfo, j_compress_ptr dstinfo,
 138              JCOPY_OPTION option));
 139
 140 #endif
 141