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