release/src/router/jpeg/transupp.h

   1 /*
   2  * transupp.h
   3  *
   4  * Copyright (C) 1997-2001, 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 /* 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  *
  61  * If both crop and a rotate/flip transform are requested, the crop is applied
  62  * last --- that is, the crop region is specified in terms of the destination
  63  * image.
  64  *
  65  * We also offer a "force to grayscale" option, which simply discards the
  66  * chrominance channels of a YCbCr image.  This is lossless in the sense that
  67  * the luminance channel is preserved exactly.  It's not the same kind of
  68  * thing as the rotate/flip transformations, but it's convenient to handle it
  69  * as part of this package, mainly because the transformation routines have to
  70  * be aware of the option to know how many components to work on.
  71  */
  72
  73
  74 /* Short forms of external names for systems with brain-damaged linkers. */
  75
  76 #ifdef NEED_SHORT_EXTERNAL_NAMES
  77 #define jtransform_parse_crop_spec      jTrParCrop
  78 #define jtransform_request_workspace    jTrRequest
  79 #define jtransform_adjust_parameters    jTrAdjust
  80 #define jtransform_execute_transform    jTrExec
  81 #define jtransform_perfect_transform    jTrPerfect
  82 #define jcopy_markers_setup             jCMrkSetup
  83 #define jcopy_markers_execute           jCMrkExec
  84 #endif /* NEED_SHORT_EXTERNAL_NAMES */
  85
  86
  87 /*
  88  * Codes for supported types of image transformations.
  89  */
  90
  91 typedef enum {
  92         JXFORM_NONE,            /* no transformation */
  93         JXFORM_FLIP_H,          /* horizontal flip */
  94         JXFORM_FLIP_V,          /* vertical flip */
  95         JXFORM_TRANSPOSE,       /* transpose across UL-to-LR axis */
  96         JXFORM_TRANSVERSE,      /* transpose across UR-to-LL axis */
  97         JXFORM_ROT_90,          /* 90-degree clockwise rotation */
  98         JXFORM_ROT_180,         /* 180-degree rotation */
  99         JXFORM_ROT_270          /* 270-degree clockwise (or 90 ccw) */
 100 } JXFORM_CODE;
 101
 102 /*
 103  * Codes for crop parameters, which can individually be unspecified,
 104  * positive, or negative.  (Negative width or height makes no sense, though.)
 105  */
 106
 107 typedef enum {
 108         JCROP_UNSET,
 109         JCROP_POS,
 110         JCROP_NEG
 111 } JCROP_CODE;
 112
 113 /*
 114  * Transform parameters struct.
 115  * NB: application must not change any elements of this struct after
 116  * calling jtransform_request_workspace.
 117  */
 118
 119 typedef struct {
 120   /* Options: set by caller */
 121   JXFORM_CODE transform;        /* image transform operator */
 122   boolean perfect;              /* if TRUE, fail if partial MCUs are requested */
 123   boolean trim;                 /* if TRUE, trim partial MCUs as needed */
 124   boolean force_grayscale;      /* if TRUE, convert color image to grayscale */
 125   boolean crop;                 /* if TRUE, crop source image */
 126
 127   /* Crop parameters: application need not set these unless crop is TRUE.
 128    * These can be filled in by jtransform_parse_crop_spec().
 129    */
 130   JDIMENSION crop_width;        /* Width of selected region */
 131   JCROP_CODE crop_width_set;
 132   JDIMENSION crop_height;       /* Height of selected region */
 133   JCROP_CODE crop_height_set;
 134   JDIMENSION crop_xoffset;      /* X offset of selected region */
 135   JCROP_CODE crop_xoffset_set;  /* (negative measures from right edge) */
 136   JDIMENSION crop_yoffset;      /* Y offset of selected region */
 137   JCROP_CODE crop_yoffset_set;  /* (negative measures from bottom edge) */
 138
 139   /* Internal workspace: caller should not touch these */
 140   int num_components;           /* # of components in workspace */
 141   jvirt_barray_ptr * workspace_coef_arrays; /* workspace for transformations */
 142   JDIMENSION output_width;      /* cropped destination dimensions */
 143   JDIMENSION output_height;
 144   JDIMENSION x_crop_offset;     /* destination crop offsets measured in iMCUs */
 145   JDIMENSION y_crop_offset;
 146   int max_h_samp_factor;        /* destination iMCU size */
 147   int max_v_samp_factor;
 148 } jpeg_transform_info;
 149
 150
 151 #if TRANSFORMS_SUPPORTED
 152
 153 /* Parse a crop specification (written in X11 geometry style) */
 154 EXTERN(boolean) jtransform_parse_crop_spec
 155         JPP((jpeg_transform_info *info, const char *spec));
 156 /* Request any required workspace */
 157 EXTERN(void) jtransform_request_workspace
 158         JPP((j_decompress_ptr srcinfo, jpeg_transform_info *info));
 159 /* Adjust output image parameters */
 160 EXTERN(jvirt_barray_ptr *) jtransform_adjust_parameters
 161         JPP((j_decompress_ptr srcinfo, j_compress_ptr dstinfo,
 162              jvirt_barray_ptr *src_coef_arrays,
 163              jpeg_transform_info *info));
 164 /* Execute the actual transformation, if any */
 165 EXTERN(void) jtransform_execute_transform
 166         JPP((j_decompress_ptr srcinfo, j_compress_ptr dstinfo,
 167              jvirt_barray_ptr *src_coef_arrays,
 168              jpeg_transform_info *info));
 169 /* Determine whether lossless transformation is perfectly
 170  * possible for a specified image and transformation.
 171  */
 172 EXTERN(boolean) jtransform_perfect_transform
 173         JPP((JDIMENSION image_width, JDIMENSION image_height,
 174              int MCU_width, int MCU_height,
 175              JXFORM_CODE transform));
 176
 177 /* jtransform_execute_transform used to be called
 178  * jtransform_execute_transformation, but some compilers complain about
 179  * routine names that long.  This macro is here to avoid breaking any
 180  * old source code that uses the original name...
 181  */
 182 #define jtransform_execute_transformation       jtransform_execute_transform
 183
 184 #endif /* TRANSFORMS_SUPPORTED */
 185
 186
 187 /*
 188  * Support for copying optional markers from source to destination file.
 189  */
 190
 191 typedef enum {
 192         JCOPYOPT_NONE,          /* copy no optional markers */
 193         JCOPYOPT_COMMENTS,      /* copy only comment (COM) markers */
 194         JCOPYOPT_ALL            /* copy all optional markers */
 195 } JCOPY_OPTION;
 196
 197 #define JCOPYOPT_DEFAULT  JCOPYOPT_COMMENTS     /* recommended default */
 198
 199 /* Setup decompression object to save desired markers in memory */
 200 EXTERN(void) jcopy_markers_setup
 201         JPP((j_decompress_ptr srcinfo, JCOPY_OPTION option));
 202 /* Copy markers saved in the given source object to the destination object */
 203 EXTERN(void) jcopy_markers_execute
 204         JPP((j_decompress_ptr srcinfo, j_compress_ptr dstinfo,
 205              JCOPY_OPTION option));