compiler/libjpeg/test/transupp.h

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