vcl/source/filter/jpeg/transupp.h

   1 /*
   2  * transupp.h
   3  *
   4  * Copyright (C) 1997-2011, Thomas G. Lane, Guido Vollbeding.
   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 /* If you happen not to want the image transform support, disable it here */
  21 #ifndef TRANSFORMS_SUPPORTED
  22 #define TRANSFORMS_SUPPORTED 1      /* 0 disables transform code */
  23 #endif
  24
  25 /*
  26  * Although rotating and flipping data expressed as DCT coefficients is not
  27  * hard, there is an asymmetry in the JPEG format specification for images
  28  * whose dimensions aren't multiples of the iMCU size.  The right and bottom
  29  * image edges are padded out to the next iMCU boundary with junk data; but
  30  * no padding is possible at the top and left edges.  If we were to flip
  31  * the whole image including the pad data, then pad garbage would become
  32  * visible at the top and/or left, and real pixels would disappear into the
  33  * pad margins --- perhaps permanently, since encoders & decoders may not
  34  * bother to preserve DCT blocks that appear to be completely outside the
  35  * nominal image area.  So, we have to exclude any partial iMCUs from the
  36  * basic transformation.
  37  *
  38  * Transpose is the only transformation that can handle partial iMCUs at the
  39  * right and bottom edges completely cleanly.  flip_h can flip partial iMCUs
  40  * at the bottom, but leaves any partial iMCUs at the right edge untouched.
  41  * Similarly flip_v leaves any partial iMCUs at the bottom edge untouched.
  42  * The other transforms are defined as combinations of these basic transforms
  43  * and process edge blocks in a way that preserves the equivalence.
  44  *
  45  * The "trim" option causes untransformable partial iMCUs to be dropped;
  46  * this is not strictly lossless, but it usually gives the best-looking
  47  * result for odd-size images.  Note that when this option is active,
  48  * the expected mathematical equivalences between the transforms may not hold.
  49  * (For example, -rot 270 -trim trims only the bottom edge, but -rot 90 -trim
  50  * followed by -rot 180 -trim trims both edges.)
  51  *
  52  * We also offer a lossless-crop option, which discards data outside a given
  53  * image region but losslessly preserves what is inside.  Like the rotate and
  54  * flip transforms, lossless crop is restricted by the JPEG format: the upper
  55  * left corner of the selected region must fall on an iMCU boundary.  If this
  56  * does not hold for the given crop parameters, we silently move the upper left
  57  * corner up and/or left to make it so, simultaneously increasing the region
  58  * dimensions to keep the lower right crop corner unchanged.  (Thus, the
  59  * output image covers at least the requested region, but may cover more.)
  60  * The adjustment of the region dimensions may be optionally disabled.
  61  *
  62  * We also provide a lossless-resize option, which is kind of a lossless-crop
  63  * operation in the DCT coefficient block domain - it discards higher-order
  64  * coefficients and losslessly preserves lower-order coefficients of a
  65  * sub-block.
  66  *
  67  * Rotate/flip transform, resize, and crop can be requested together in a
  68  * single invocation.  The crop is applied last --- that is, the crop region
  69  * is specified in terms of the destination image after transform/resize.
  70  *
  71  * We also offer a "force to grayscale" option, which simply discards the
  72  * chrominance channels of a YCbCr image.  This is lossless in the sense that
  73  * the luminance channel is preserved exactly.  It's not the same kind of
  74  * thing as the rotate/flip transformations, but it's convenient to handle it
  75  * as part of this package, mainly because the transformation routines have to
  76  * be aware of the option to know how many components to work on.
  77  */
  78
  79 /* Short forms of external names for systems with brain-damaged linkers. */
  80
  81 #ifdef NEED_SHORT_EXTERNAL_NAMES
  82 #define jtransform_parse_crop_spec  jTrParCrop
  83 #define jtransform_request_workspace    jTrRequest
  84 #define jtransform_adjust_parameters    jTrAdjust
  85 #define jtransform_execute_transform    jTrExec
  86 #define jtransform_perfect_transform    jTrPerfect
  87 #define jcopy_markers_setup     jCMrkSetup
  88 #define jcopy_markers_execute       jCMrkExec
  89 #endif /* NEED_SHORT_EXTERNAL_NAMES */
  90
  91 /*
  92  * Codes for supported types of image transformations.
  93  */
  94
  95 typedef enum {
  96     JXFORM_NONE,        /* no transformation */
  97     JXFORM_FLIP_H,      /* horizontal flip */
  98     JXFORM_FLIP_V,      /* vertical flip */
  99     JXFORM_TRANSPOSE,   /* transpose across UL-to-LR axis */
 100     JXFORM_TRANSVERSE,  /* transpose across UR-to-LL axis */
 101     JXFORM_ROT_90,      /* 90-degree clockwise rotation */
 102     JXFORM_ROT_180,     /* 180-degree rotation */
 103     JXFORM_ROT_270      /* 270-degree clockwise (or 90 ccw) */
 104 } JXFORM_CODE;
 105
 106 /*
 107  * Codes for crop parameters, which can individually be unspecified,
 108  * positive or negative for xoffset or yoffset,
 109  * positive or forced for width or height.
 110  */
 111
 112 typedef enum {
 113         JCROP_UNSET,
 114         JCROP_POS,
 115         JCROP_NEG,
 116         JCROP_FORCE
 117 } JCROP_CODE;
 118
 119 /*
 120  * Transform parameters struct.
 121  * NB: application must not change any elements of this struct after
 122  * calling jtransform_request_workspace.
 123  */
 124
 125 typedef struct {
 126   /* Options: set by caller */
 127   JXFORM_CODE transform;    /* image transform operator */
 128   boolean perfect;      /* if TRUE, fail if partial MCUs are requested */
 129   boolean trim;         /* if TRUE, trim partial MCUs as needed */
 130   boolean force_grayscale;  /* if TRUE, convert color image to grayscale */
 131   boolean crop;         /* if TRUE, crop source image */
 132   boolean slow_hflip;  /* For best performance, the JXFORM_FLIP_H transform
 133                           normally modifies the source coefficients in place.
 134                           Setting this to TRUE will instead use a slower,
 135                           double-buffered algorithm, which leaves the source
 136                           coefficients intact (necessary if other transformed
 137                           images must be generated from the same set of
 138                           coefficients. */
 139
 140   /* Crop parameters: application need not set these unless crop is TRUE.
 141    * These can be filled in by jtransform_parse_crop_spec().
 142    */
 143   JDIMENSION crop_width;    /* Width of selected region */
 144   JCROP_CODE crop_width_set;    /* (forced disables adjustment) */
 145   JDIMENSION crop_height;   /* Height of selected region */
 146   JCROP_CODE crop_height_set;   /* (forced disables adjustment) */
 147   JDIMENSION crop_xoffset;  /* X offset of selected region */
 148   JCROP_CODE crop_xoffset_set;  /* (negative measures from right edge) */
 149   JDIMENSION crop_yoffset;  /* Y offset of selected region */
 150   JCROP_CODE crop_yoffset_set;  /* (negative measures from bottom edge) */
 151
 152   /* Internal workspace: caller should not touch these */
 153   int num_components;       /* # of components in workspace */
 154   jvirt_barray_ptr * workspace_coef_arrays; /* workspace for transformations */
 155   JDIMENSION output_width;  /* cropped destination dimensions */
 156   JDIMENSION output_height;
 157   JDIMENSION x_crop_offset; /* destination crop offsets measured in iMCUs */
 158   JDIMENSION y_crop_offset;
 159   int iMCU_sample_width;    /* destination iMCU size */
 160   int iMCU_sample_height;
 161 } jpeg_transform_info;
 162
 163 #if TRANSFORMS_SUPPORTED
 164
 165 /* Request any required workspace */
 166 EXTERN(boolean) jtransform_request_workspace
 167     (j_decompress_ptr srcinfo, jpeg_transform_info *info);
 168 /* Adjust output image parameters */
 169 EXTERN(jvirt_barray_ptr *) jtransform_adjust_parameters
 170     (j_decompress_ptr srcinfo, j_compress_ptr dstinfo,
 171          jvirt_barray_ptr *src_coef_arrays,
 172          jpeg_transform_info *info);
 173 /* Execute the actual transformation, if any */
 174 EXTERN(void) jtransform_execute_transform
 175     (j_decompress_ptr srcinfo, j_compress_ptr dstinfo,
 176          jvirt_barray_ptr *src_coef_arrays,
 177          jpeg_transform_info *info);
 178 /* Determine whether lossless transformation is perfectly
 179  * possible for a specified image and transformation.
 180  */
 181 EXTERN(boolean) jtransform_perfect_transform
 182     (JDIMENSION image_width, JDIMENSION image_height,
 183          int MCU_width, int MCU_height,
 184          JXFORM_CODE transform);
 185
 186 /* jtransform_execute_transform used to be called
 187  * jtransform_execute_transformation, but some compilers complain about
 188  * routine names that long.  This macro is here to avoid breaking any
 189  * old source code that uses the original name...
 190  */
 191 #define jtransform_execute_transformation   jtransform_execute_transform
 192
 193 #endif /* TRANSFORMS_SUPPORTED */
 194
 195 /*
 196  * Support for copying optional markers from source to destination file.
 197  */
 198
 199 typedef enum {
 200     JCOPYOPT_NONE,      /* copy no optional markers */
 201     JCOPYOPT_COMMENTS,  /* copy only comment (COM) markers */
 202     JCOPYOPT_ALL        /* copy all optional markers */
 203 } JCOPY_OPTION;
 204
 205
 206 /* Setup decompression object to save desired markers in memory */
 207 EXTERN(void) jcopy_markers_setup
 208     (j_decompress_ptr srcinfo, JCOPY_OPTION option);
 209 /* Copy markers saved in the given source object to the destination object */
 210 EXTERN(void) jcopy_markers_execute
 211     (j_decompress_ptr srcinfo, j_compress_ptr dstinfo,
 212          JCOPY_OPTION option);