transupp.h 9.8 KB

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  1. /*
  2. * transupp.h
  3. *
  4. * This file was part of the Independent JPEG Group's software:
  5. * Copyright (C) 1997-2011, Thomas G. Lane, Guido Vollbeding.
  6. * libjpeg-turbo Modifications:
  7. * Copyright (C) 2017, D. R. Commander.
  8. * For conditions of distribution and use, see the accompanying README.ijg
  9. * file.
  10. *
  11. * This file contains declarations for image transformation routines and
  12. * other utility code used by the jpegtran sample application. These are
  13. * NOT part of the core JPEG library. But we keep these routines separate
  14. * from jpegtran.c to ease the task of maintaining jpegtran-like programs
  15. * that have other user interfaces.
  16. *
  17. * NOTE: all the routines declared here have very specific requirements
  18. * about when they are to be executed during the reading and writing of the
  19. * source and destination files. See the comments in transupp.c, or see
  20. * jpegtran.c for an example of correct usage.
  21. */
  22. /* If you happen not to want the image transform support, disable it here */
  23. #ifndef TRANSFORMS_SUPPORTED
  24. #define TRANSFORMS_SUPPORTED 1 /* 0 disables transform code */
  25. #endif
  26. /*
  27. * Although rotating and flipping data expressed as DCT coefficients is not
  28. * hard, there is an asymmetry in the JPEG format specification for images
  29. * whose dimensions aren't multiples of the iMCU size. The right and bottom
  30. * image edges are padded out to the next iMCU boundary with junk data; but
  31. * no padding is possible at the top and left edges. If we were to flip
  32. * the whole image including the pad data, then pad garbage would become
  33. * visible at the top and/or left, and real pixels would disappear into the
  34. * pad margins --- perhaps permanently, since encoders & decoders may not
  35. * bother to preserve DCT blocks that appear to be completely outside the
  36. * nominal image area. So, we have to exclude any partial iMCUs from the
  37. * basic transformation.
  38. *
  39. * Transpose is the only transformation that can handle partial iMCUs at the
  40. * right and bottom edges completely cleanly. flip_h can flip partial iMCUs
  41. * at the bottom, but leaves any partial iMCUs at the right edge untouched.
  42. * Similarly flip_v leaves any partial iMCUs at the bottom edge untouched.
  43. * The other transforms are defined as combinations of these basic transforms
  44. * and process edge blocks in a way that preserves the equivalence.
  45. *
  46. * The "trim" option causes untransformable partial iMCUs to be dropped;
  47. * this is not strictly lossless, but it usually gives the best-looking
  48. * result for odd-size images. Note that when this option is active,
  49. * the expected mathematical equivalences between the transforms may not hold.
  50. * (For example, -rot 270 -trim trims only the bottom edge, but -rot 90 -trim
  51. * followed by -rot 180 -trim trims both edges.)
  52. *
  53. * We also offer a lossless-crop option, which discards data outside a given
  54. * image region but losslessly preserves what is inside. Like the rotate and
  55. * flip transforms, lossless crop is restricted by the JPEG format: the upper
  56. * left corner of the selected region must fall on an iMCU boundary. If this
  57. * does not hold for the given crop parameters, we silently move the upper left
  58. * corner up and/or left to make it so, simultaneously increasing the region
  59. * dimensions to keep the lower right crop corner unchanged. (Thus, the
  60. * output image covers at least the requested region, but may cover more.)
  61. * The adjustment of the region dimensions may be optionally disabled.
  62. *
  63. * We also provide a lossless-resize option, which is kind of a lossless-crop
  64. * operation in the DCT coefficient block domain - it discards higher-order
  65. * coefficients and losslessly preserves lower-order coefficients of a
  66. * sub-block.
  67. *
  68. * Rotate/flip transform, resize, and crop can be requested together in a
  69. * single invocation. The crop is applied last --- that is, the crop region
  70. * is specified in terms of the destination image after transform/resize.
  71. *
  72. * We also offer a "force to grayscale" option, which simply discards the
  73. * chrominance channels of a YCbCr image. This is lossless in the sense that
  74. * the luminance channel is preserved exactly. It's not the same kind of
  75. * thing as the rotate/flip transformations, but it's convenient to handle it
  76. * as part of this package, mainly because the transformation routines have to
  77. * be aware of the option to know how many components to work on.
  78. */
  79. /*
  80. * Codes for supported types of image transformations.
  81. */
  82. typedef enum {
  83. JXFORM_NONE, /* no transformation */
  84. JXFORM_FLIP_H, /* horizontal flip */
  85. JXFORM_FLIP_V, /* vertical flip */
  86. JXFORM_TRANSPOSE, /* transpose across UL-to-LR axis */
  87. JXFORM_TRANSVERSE, /* transpose across UR-to-LL axis */
  88. JXFORM_ROT_90, /* 90-degree clockwise rotation */
  89. JXFORM_ROT_180, /* 180-degree rotation */
  90. JXFORM_ROT_270 /* 270-degree clockwise (or 90 ccw) */
  91. } JXFORM_CODE;
  92. /*
  93. * Codes for crop parameters, which can individually be unspecified,
  94. * positive or negative for xoffset or yoffset,
  95. * positive or forced for width or height.
  96. */
  97. typedef enum {
  98. JCROP_UNSET,
  99. JCROP_POS,
  100. JCROP_NEG,
  101. JCROP_FORCE
  102. } JCROP_CODE;
  103. /*
  104. * Transform parameters struct.
  105. * NB: application must not change any elements of this struct after
  106. * calling jtransform_request_workspace.
  107. */
  108. typedef struct {
  109. /* Options: set by caller */
  110. JXFORM_CODE transform; /* image transform operator */
  111. boolean perfect; /* if TRUE, fail if partial MCUs are requested */
  112. boolean trim; /* if TRUE, trim partial MCUs as needed */
  113. boolean force_grayscale; /* if TRUE, convert color image to grayscale */
  114. boolean crop; /* if TRUE, crop source image */
  115. boolean slow_hflip; /* For best performance, the JXFORM_FLIP_H transform
  116. normally modifies the source coefficients in place.
  117. Setting this to TRUE will instead use a slower,
  118. double-buffered algorithm, which leaves the source
  119. coefficients in tact (necessary if other transformed
  120. images must be generated from the same set of
  121. coefficients. */
  122. /* Crop parameters: application need not set these unless crop is TRUE.
  123. * These can be filled in by jtransform_parse_crop_spec().
  124. */
  125. JDIMENSION crop_width; /* Width of selected region */
  126. JCROP_CODE crop_width_set; /* (forced disables adjustment) */
  127. JDIMENSION crop_height; /* Height of selected region */
  128. JCROP_CODE crop_height_set; /* (forced disables adjustment) */
  129. JDIMENSION crop_xoffset; /* X offset of selected region */
  130. JCROP_CODE crop_xoffset_set; /* (negative measures from right edge) */
  131. JDIMENSION crop_yoffset; /* Y offset of selected region */
  132. JCROP_CODE crop_yoffset_set; /* (negative measures from bottom edge) */
  133. /* Internal workspace: caller should not touch these */
  134. int num_components; /* # of components in workspace */
  135. jvirt_barray_ptr *workspace_coef_arrays; /* workspace for transformations */
  136. JDIMENSION output_width; /* cropped destination dimensions */
  137. JDIMENSION output_height;
  138. JDIMENSION x_crop_offset; /* destination crop offsets measured in iMCUs */
  139. JDIMENSION y_crop_offset;
  140. int iMCU_sample_width; /* destination iMCU size */
  141. int iMCU_sample_height;
  142. } jpeg_transform_info;
  143. #if TRANSFORMS_SUPPORTED
  144. /* Parse a crop specification (written in X11 geometry style) */
  145. EXTERN(boolean) jtransform_parse_crop_spec(jpeg_transform_info *info,
  146. const char *spec);
  147. /* Request any required workspace */
  148. EXTERN(boolean) jtransform_request_workspace(j_decompress_ptr srcinfo,
  149. jpeg_transform_info *info);
  150. /* Adjust output image parameters */
  151. EXTERN(jvirt_barray_ptr *) jtransform_adjust_parameters
  152. (j_decompress_ptr srcinfo, j_compress_ptr dstinfo,
  153. jvirt_barray_ptr *src_coef_arrays, jpeg_transform_info *info);
  154. /* Execute the actual transformation, if any */
  155. EXTERN(void) jtransform_execute_transform(j_decompress_ptr srcinfo,
  156. j_compress_ptr dstinfo,
  157. jvirt_barray_ptr *src_coef_arrays,
  158. jpeg_transform_info *info);
  159. /* Determine whether lossless transformation is perfectly
  160. * possible for a specified image and transformation.
  161. */
  162. EXTERN(boolean) jtransform_perfect_transform(JDIMENSION image_width,
  163. JDIMENSION image_height,
  164. int MCU_width, int MCU_height,
  165. JXFORM_CODE transform);
  166. /* jtransform_execute_transform used to be called
  167. * jtransform_execute_transformation, but some compilers complain about
  168. * routine names that long. This macro is here to avoid breaking any
  169. * old source code that uses the original name...
  170. */
  171. #define jtransform_execute_transformation jtransform_execute_transform
  172. #endif /* TRANSFORMS_SUPPORTED */
  173. /*
  174. * Support for copying optional markers from source to destination file.
  175. */
  176. typedef enum {
  177. JCOPYOPT_NONE, /* copy no optional markers */
  178. JCOPYOPT_COMMENTS, /* copy only comment (COM) markers */
  179. JCOPYOPT_ALL, /* copy all optional markers */
  180. JCOPYOPT_ALL_EXCEPT_ICC /* copy all optional markers except APP2 */
  181. } JCOPY_OPTION;
  182. #define JCOPYOPT_DEFAULT JCOPYOPT_COMMENTS /* recommended default */
  183. /* Setup decompression object to save desired markers in memory */
  184. EXTERN(void) jcopy_markers_setup(j_decompress_ptr srcinfo,
  185. JCOPY_OPTION option);
  186. /* Copy markers saved in the given source object to the destination object */
  187. EXTERN(void) jcopy_markers_execute(j_decompress_ptr srcinfo,
  188. j_compress_ptr dstinfo,
  189. JCOPY_OPTION option);