Diff: includes/transupp.h

Revision:

0:791a779d6220

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/includes/transupp.h	Mon Jul 31 09:16:35 2017 +0000
@@ -0,0 +1,219 @@
+/*
+ * transupp.h
+ *
+ * Copyright (C) 1997-2013, Thomas G. Lane, Guido Vollbeding.
+ * This file is part of the Independent JPEG Group's software.
+ * For conditions of distribution and use, see the accompanying README file.
+ *
+ * This file contains declarations for image transformation routines and
+ * other utility code used by the jpegtran sample application.  These are
+ * NOT part of the core JPEG library.  But we keep these routines separate
+ * from jpegtran.c to ease the task of maintaining jpegtran-like programs
+ * that have other user interfaces.
+ *
+ * NOTE: all the routines declared here have very specific requirements
+ * about when they are to be executed during the reading and writing of the
+ * source and destination files.  See the comments in transupp.c, or see
+ * jpegtran.c for an example of correct usage.
+ */
+
+/* If you happen not to want the image transform support, disable it here */
+#ifndef TRANSFORMS_SUPPORTED
+#define TRANSFORMS_SUPPORTED 1		/* 0 disables transform code */
+#endif
+
+/*
+ * Although rotating and flipping data expressed as DCT coefficients is not
+ * hard, there is an asymmetry in the JPEG format specification for images
+ * whose dimensions aren't multiples of the iMCU size.  The right and bottom
+ * image edges are padded out to the next iMCU boundary with junk data; but
+ * no padding is possible at the top and left edges.  If we were to flip
+ * the whole image including the pad data, then pad garbage would become
+ * visible at the top and/or left, and real pixels would disappear into the
+ * pad margins --- perhaps permanently, since encoders & decoders may not
+ * bother to preserve DCT blocks that appear to be completely outside the
+ * nominal image area.  So, we have to exclude any partial iMCUs from the
+ * basic transformation.
+ *
+ * Transpose is the only transformation that can handle partial iMCUs at the
+ * right and bottom edges completely cleanly.  flip_h can flip partial iMCUs
+ * at the bottom, but leaves any partial iMCUs at the right edge untouched.
+ * Similarly flip_v leaves any partial iMCUs at the bottom edge untouched.
+ * The other transforms are defined as combinations of these basic transforms
+ * and process edge blocks in a way that preserves the equivalence.
+ *
+ * The "trim" option causes untransformable partial iMCUs to be dropped;
+ * this is not strictly lossless, but it usually gives the best-looking
+ * result for odd-size images.  Note that when this option is active,
+ * the expected mathematical equivalences between the transforms may not hold.
+ * (For example, -rot 270 -trim trims only the bottom edge, but -rot 90 -trim
+ * followed by -rot 180 -trim trims both edges.)
+ *
+ * We also offer a lossless-crop option, which discards data outside a given
+ * image region but losslessly preserves what is inside.  Like the rotate and
+ * flip transforms, lossless crop is restricted by the current JPEG format: the
+ * upper left corner of the selected region must fall on an iMCU boundary.  If
+ * this does not hold for the given crop parameters, we silently move the upper
+ * left corner up and/or left to make it so, simultaneously increasing the
+ * region dimensions to keep the lower right crop corner unchanged.  (Thus, the
+ * output image covers at least the requested region, but may cover more.)
+ * The adjustment of the region dimensions may be optionally disabled.
+ *
+ * A complementary lossless-wipe option is provided to discard (gray out) data
+ * inside a given image region while losslessly preserving what is outside.
+ *
+ * We also provide a lossless-resize option, which is kind of a lossless-crop
+ * operation in the DCT coefficient block domain - it discards higher-order
+ * coefficients and losslessly preserves lower-order coefficients of a
+ * sub-block.
+ *
+ * Rotate/flip transform, resize, and crop can be requested together in a
+ * single invocation.  The crop is applied last --- that is, the crop region
+ * is specified in terms of the destination image after transform/resize.
+ *
+ * We also offer a "force to grayscale" option, which simply discards the
+ * chrominance channels of a YCbCr image.  This is lossless in the sense that
+ * the luminance channel is preserved exactly.  It's not the same kind of
+ * thing as the rotate/flip transformations, but it's convenient to handle it
+ * as part of this package, mainly because the transformation routines have to
+ * be aware of the option to know how many components to work on.
+ */
+
+
+/* Short forms of external names for systems with brain-damaged linkers. */
+
+#ifdef NEED_SHORT_EXTERNAL_NAMES
+#define jtransform_parse_crop_spec	jTrParCrop
+#define jtransform_request_workspace	jTrRequest
+#define jtransform_adjust_parameters	jTrAdjust
+#define jtransform_execute_transform	jTrExec
+#define jtransform_perfect_transform	jTrPerfect
+#define jcopy_markers_setup		jCMrkSetup
+#define jcopy_markers_execute		jCMrkExec
+#endif /* NEED_SHORT_EXTERNAL_NAMES */
+
+
+/*
+ * Codes for supported types of image transformations.
+ */
+
+typedef enum {
+	JXFORM_NONE,		/* no transformation */
+	JXFORM_FLIP_H,		/* horizontal flip */
+	JXFORM_FLIP_V,		/* vertical flip */
+	JXFORM_TRANSPOSE,	/* transpose across UL-to-LR axis */
+	JXFORM_TRANSVERSE,	/* transpose across UR-to-LL axis */
+	JXFORM_ROT_90,		/* 90-degree clockwise rotation */
+	JXFORM_ROT_180,		/* 180-degree rotation */
+	JXFORM_ROT_270,		/* 270-degree clockwise (or 90 ccw) */
+	JXFORM_WIPE		/* wipe */
+} JXFORM_CODE;
+
+/*
+ * Codes for crop parameters, which can individually be unspecified,
+ * positive or negative for xoffset or yoffset,
+ * positive or forced for width or height.
+ */
+
+typedef enum {
+        JCROP_UNSET,
+        JCROP_POS,
+        JCROP_NEG,
+        JCROP_FORCE
+} JCROP_CODE;
+
+/*
+ * Transform parameters struct.
+ * NB: application must not change any elements of this struct after
+ * calling jtransform_request_workspace.
+ */
+
+typedef struct {
+  /* Options: set by caller */
+  JXFORM_CODE transform;	/* image transform operator */
+  boolean perfect;		/* if TRUE, fail if partial MCUs are requested */
+  boolean trim;			/* if TRUE, trim partial MCUs as needed */
+  boolean force_grayscale;	/* if TRUE, convert color image to grayscale */
+  boolean crop;			/* if TRUE, crop or wipe source image */
+
+  /* Crop parameters: application need not set these unless crop is TRUE.
+   * These can be filled in by jtransform_parse_crop_spec().
+   */
+  JDIMENSION crop_width;	/* Width of selected region */
+  JCROP_CODE crop_width_set;	/* (forced disables adjustment) */
+  JDIMENSION crop_height;	/* Height of selected region */
+  JCROP_CODE crop_height_set;	/* (forced disables adjustment) */
+  JDIMENSION crop_xoffset;	/* X offset of selected region */
+  JCROP_CODE crop_xoffset_set;	/* (negative measures from right edge) */
+  JDIMENSION crop_yoffset;	/* Y offset of selected region */
+  JCROP_CODE crop_yoffset_set;	/* (negative measures from bottom edge) */
+
+  /* Internal workspace: caller should not touch these */
+  int num_components;		/* # of components in workspace */
+  jvirt_barray_ptr * workspace_coef_arrays; /* workspace for transformations */
+  JDIMENSION output_width;	/* cropped destination dimensions */
+  JDIMENSION output_height;
+  JDIMENSION x_crop_offset;	/* destination crop offsets measured in iMCUs */
+  JDIMENSION y_crop_offset;
+  JDIMENSION drop_width;	/* drop/wipe dimensions measured in iMCUs */
+  JDIMENSION drop_height;
+  int iMCU_sample_width;	/* destination iMCU size */
+  int iMCU_sample_height;
+} jpeg_transform_info;
+
+
+#if TRANSFORMS_SUPPORTED
+
+/* Parse a crop specification (written in X11 geometry style) */
+EXTERN(boolean) jtransform_parse_crop_spec
+	JPP((jpeg_transform_info *info, const char *spec));
+/* Request any required workspace */
+EXTERN(boolean) jtransform_request_workspace
+	JPP((j_decompress_ptr srcinfo, jpeg_transform_info *info));
+/* Adjust output image parameters */
+EXTERN(jvirt_barray_ptr *) jtransform_adjust_parameters
+	JPP((j_decompress_ptr srcinfo, j_compress_ptr dstinfo,
+	     jvirt_barray_ptr *src_coef_arrays,
+	     jpeg_transform_info *info));
+/* Execute the actual transformation, if any */
+EXTERN(void) jtransform_execute_transform
+	JPP((j_decompress_ptr srcinfo, j_compress_ptr dstinfo,
+	     jvirt_barray_ptr *src_coef_arrays,
+	     jpeg_transform_info *info));
+/* Determine whether lossless transformation is perfectly
+ * possible for a specified image and transformation.
+ */
+EXTERN(boolean) jtransform_perfect_transform
+	JPP((JDIMENSION image_width, JDIMENSION image_height,
+	     int MCU_width, int MCU_height,
+	     JXFORM_CODE transform));
+
+/* jtransform_execute_transform used to be called
+ * jtransform_execute_transformation, but some compilers complain about
+ * routine names that long.  This macro is here to avoid breaking any
+ * old source code that uses the original name...
+ */
+#define jtransform_execute_transformation	jtransform_execute_transform
+
+#endif /* TRANSFORMS_SUPPORTED */
+
+
+/*
+ * Support for copying optional markers from source to destination file.
+ */
+
+typedef enum {
+	JCOPYOPT_NONE,		/* copy no optional markers */
+	JCOPYOPT_COMMENTS,	/* copy only comment (COM) markers */
+	JCOPYOPT_ALL		/* copy all optional markers */
+} JCOPY_OPTION;
+
+#define JCOPYOPT_DEFAULT  JCOPYOPT_COMMENTS	/* recommended default */
+
+/* Setup decompression object to save desired markers in memory */
+EXTERN(void) jcopy_markers_setup
+	JPP((j_decompress_ptr srcinfo, JCOPY_OPTION option));
+/* Copy markers saved in the given source object to the destination object */
+EXTERN(void) jcopy_markers_execute
+	JPP((j_decompress_ptr srcinfo, j_compress_ptr dstinfo,
+	     JCOPY_OPTION option));