1 /*

     2  * jdsample.c

     3  *

     4  * Copyright (C) 1991-1996, 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 upsampling routines.

     9  *

    10  * Upsampling input data is counted in "row groups".  A row group

    11  * is defined to be (v_samp_factor * DCT_scaled_size / min_DCT_scaled_size)

    12  * sample rows of each component.  Upsampling will normally produce

    13  * max_v_samp_factor pixel rows from each row group (but this could vary

    14  * if the upsampler is applying a scale factor of its own).

    15  *

    16  * An excellent reference for image resampling is

    17  *   Digital Image Warping, George Wolberg, 1990.

    18  *   Pub. by IEEE Computer Society Press, Los Alamitos, CA. ISBN 0-8186-8944-7.

    19  */

    20 

    21 #define JPEG_INTERNALS

    22 #include "jinclude.h"

    23 #include "jpeglib.h"

    24 

    25 

    26 /* Pointer to routine to upsample a single component */

    27 typedef JMETHOD(void, upsample1_ptr,

    28 		(j_decompress_ptr cinfo, jpeg_component_info * compptr,

    29 		 JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr));

    30 

    31 /* Private subobject */

    32 

    33 typedef struct {

    34   struct jpeg_upsampler pub;	/* public fields */

    35 

    36   /* Color conversion buffer.  When using separate upsampling and color

    37    * conversion steps, this buffer holds one upsampled row group until it

    38    * has been color converted and output.

    39    * Note: we do not allocate any storage for component(s) which are full-size,

    40    * ie do not need rescaling.  The corresponding entry of color_buf[] is

    41    * simply set to point to the input data array, thereby avoiding copying.

    42    */

    43   JSAMPARRAY color_buf[MAX_COMPONENTS];

    44 

    45   /* Per-component upsampling method pointers */

    46   upsample1_ptr methods[MAX_COMPONENTS];

    47 

    48   int next_row_out;		/* counts rows emitted from color_buf */

    49   JDIMENSION rows_to_go;	/* counts rows remaining in image */

    50 

    51   /* Height of an input row group for each component. */

    52   int rowgroup_height[MAX_COMPONENTS];

    53 

    54   /* These arrays save pixel expansion factors so that int_expand need not

    55    * recompute them each time.  They are unused for other upsampling methods.

    56    */

    57   UINT8 h_expand[MAX_COMPONENTS];

    58   UINT8 v_expand[MAX_COMPONENTS];

    59 } my_upsampler;

    60 

    61 typedef my_upsampler * my_upsample_ptr;

    62 

    63 

    64 /*

    65  * Initialize for an upsampling pass.

    66  */

    67 

    68 METHODDEF(void)

    69 start_pass_upsample (j_decompress_ptr cinfo)

    70 {

    71   my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;

    72 

    73   /* Mark the conversion buffer empty */

    74   upsample->next_row_out = cinfo->max_v_samp_factor;

    75   /* Initialize total-height counter for detecting bottom of image */

    76   upsample->rows_to_go = cinfo->output_height;

    77 }

    78 

    79 

    80 /*

    81  * Control routine to do upsampling (and color conversion).

    82  *

    83  * In this version we upsample each component independently.

    84  * We upsample one row group into the conversion buffer, then apply

    85  * color conversion a row at a time.

    86  */

    87 

    88 METHODDEF(void)

    89 sep_upsample (j_decompress_ptr cinfo,

    90 	      JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr,

    91 	      JDIMENSION in_row_groups_avail,

    92 	      JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,

    93 	      JDIMENSION out_rows_avail)

    94 {

    95   my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;

    96   int ci;

    97   jpeg_component_info * compptr;

    98   JDIMENSION num_rows;

    99 

   100   /* Fill the conversion buffer, if it's empty */

   101   if (upsample->next_row_out >= cinfo->max_v_samp_factor) {

   102     for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;

   103 	 ci++, compptr++) {

   104       /* Invoke per-component upsample method.  Notice we pass a POINTER

   105        * to color_buf[ci], so that fullsize_upsample can change it.

   106        */

   107       (*upsample->methods[ci]) (cinfo, compptr,

   108 	input_buf[ci] + (*in_row_group_ctr * upsample->rowgroup_height[ci]),

   109 	upsample->color_buf + ci);

   110     }

   111     upsample->next_row_out = 0;

   112   }

   113 

   114   /* Color-convert and emit rows */

   115 

   116   /* How many we have in the buffer: */

   117   num_rows = (JDIMENSION) (cinfo->max_v_samp_factor - upsample->next_row_out);

   118   /* Not more than the distance to the end of the image.  Need this test

   119    * in case the image height is not a multiple of max_v_samp_factor:

   120    */

   121   if (num_rows > upsample->rows_to_go) 

   122     num_rows = upsample->rows_to_go;

   123   /* And not more than what the client can accept: */

   124   out_rows_avail -= *out_row_ctr;

   125   if (num_rows > out_rows_avail)

   126     num_rows = out_rows_avail;

   127 

   128   (*cinfo->cconvert->color_convert) (cinfo, upsample->color_buf,

   129 				     (JDIMENSION) upsample->next_row_out,

   130 				     output_buf + *out_row_ctr,

   131 				     (int) num_rows);

   132 

   133   /* Adjust counts */

   134   *out_row_ctr += num_rows;

   135   upsample->rows_to_go -= num_rows;

   136   upsample->next_row_out += num_rows;

   137   /* When the buffer is emptied, declare this input row group consumed */

   138   if (upsample->next_row_out >= cinfo->max_v_samp_factor)

   139     (*in_row_group_ctr)++;

   140 }

   141 

   142 

   143 /*

   144  * These are the routines invoked by sep_upsample to upsample pixel values

   145  * of a single component.  One row group is processed per call.

   146  */

   147 

   148 

   149 /*

   150  * For full-size components, we just make color_buf[ci] point at the

   151  * input buffer, and thus avoid copying any data.  Note that this is

   152  * safe only because sep_upsample doesn't declare the input row group

   153  * "consumed" until we are done color converting and emitting it.

   154  */

   155 

   156 METHODDEF(void)

   157 fullsize_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,

   158 		   JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)

   159 {

   160   *output_data_ptr = input_data;

   161 }

   162 

   163 

   164 /*

   165  * This is a no-op version used for "uninteresting" components.

   166  * These components will not be referenced by color conversion.

   167  */

   168 

   169 METHODDEF(void)

   170 noop_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,

   171 	       JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)

   172 {

   173   *output_data_ptr = NULL;	/* safety check */

   174 }

   175 

   176 

   177 /*

   178  * This version handles any integral sampling ratios.

   179  * This is not used for typical JPEG files, so it need not be fast.

   180  * Nor, for that matter, is it particularly accurate: the algorithm is

   181  * simple replication of the input pixel onto the corresponding output

   182  * pixels.  The hi-falutin sampling literature refers to this as a

   183  * "box filter".  A box filter tends to introduce visible artifacts,

   184  * so if you are actually going to use 3:1 or 4:1 sampling ratios

   185  * you would be well advised to improve this code.

   186  */

   187 

   188 METHODDEF(void)

   189 int_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,

   190 	      JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)

   191 {

   192   my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;

   193   JSAMPARRAY output_data = *output_data_ptr;

   194   register JSAMPROW inptr, outptr;

   195   register JSAMPLE invalue;

   196   register int h;

   197   JSAMPROW outend;

   198   int h_expand, v_expand;

   199   int inrow, outrow;

   200 

   201   h_expand = upsample->h_expand[compptr->component_index];

   202   v_expand = upsample->v_expand[compptr->component_index];

   203 

   204   inrow = outrow = 0;

   205   while (outrow < cinfo->max_v_samp_factor) {

   206     /* Generate one output row with proper horizontal expansion */

   207     inptr = input_data[inrow];

   208     outptr = output_data[outrow];

   209     outend = outptr + cinfo->output_width;

   210     while (outptr < outend) {

   211       invalue = *inptr++;	/* don't need GETJSAMPLE() here */

   212       for (h = h_expand; h > 0; h--) {

   213 	*outptr++ = invalue;

   214       }

   215     }

   216     /* Generate any additional output rows by duplicating the first one */

   217     if (v_expand > 1) {

   218       jcopy_sample_rows(output_data, outrow, output_data, outrow+1,

   219 			v_expand-1, cinfo->output_width);

   220     }

   221     inrow++;

   222     outrow += v_expand;

   223   }

   224 }

   225 

   226 

   227 /*

   228  * Fast processing for the common case of 2:1 horizontal and 1:1 vertical.

   229  * It's still a box filter.

   230  */

   231 

   232 METHODDEF(void)

   233 h2v1_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,

   234 	       JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)

   235 {

   236   JSAMPARRAY output_data = *output_data_ptr;

   237   register JSAMPROW inptr, outptr;

   238   register JSAMPLE invalue;

   239   JSAMPROW outend;

   240   int inrow;

   241 

   242   for (inrow = 0; inrow < cinfo->max_v_samp_factor; inrow++) {

   243     inptr = input_data[inrow];

   244     outptr = output_data[inrow];

   245     outend = outptr + cinfo->output_width;

   246     while (outptr < outend) {

   247       invalue = *inptr++;	/* don't need GETJSAMPLE() here */

   248       *outptr++ = invalue;

   249       *outptr++ = invalue;

   250     }

   251   }

   252 }

   253 

   254 

   255 /*

   256  * Fast processing for the common case of 2:1 horizontal and 2:1 vertical.

   257  * It's still a box filter.

   258  */

   259 

   260 METHODDEF(void)

   261 h2v2_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,

   262 	       JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)

   263 {

   264   JSAMPARRAY output_data = *output_data_ptr;

   265   register JSAMPROW inptr, outptr;

   266   register JSAMPLE invalue;

   267   JSAMPROW outend;

   268   int inrow, outrow;

   269 

   270   inrow = outrow = 0;

   271   while (outrow < cinfo->max_v_samp_factor) {

   272     inptr = input_data[inrow];

   273     outptr = output_data[outrow];

   274     outend = outptr + cinfo->output_width;

   275     while (outptr < outend) {

   276       invalue = *inptr++;	/* don't need GETJSAMPLE() here */

   277       *outptr++ = invalue;

   278       *outptr++ = invalue;

   279     }

   280     jcopy_sample_rows(output_data, outrow, output_data, outrow+1,

   281 		      1, cinfo->output_width);

   282     inrow++;

   283     outrow += 2;

   284   }

   285 }

   286 

   287 

   288 /*

   289  * Fancy processing for the common case of 2:1 horizontal and 1:1 vertical.

   290  *

   291  * The upsampling algorithm is linear interpolation between pixel centers,

   292  * also known as a "triangle filter".  This is a good compromise between

   293  * speed and visual quality.  The centers of the output pixels are 1/4 and 3/4

   294  * of the way between input pixel centers.

   295  *

   296  * A note about the "bias" calculations: when rounding fractional values to

   297  * integer, we do not want to always round 0.5 up to the next integer.

   298  * If we did that, we'd introduce a noticeable bias towards larger values.

   299  * Instead, this code is arranged so that 0.5 will be rounded up or down at

   300  * alternate pixel locations (a simple ordered dither pattern).

   301  */

   302 

   303 METHODDEF(void)

   304 h2v1_fancy_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,

   305 		     JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)

   306 {

   307   JSAMPARRAY output_data = *output_data_ptr;

   308   register JSAMPROW inptr, outptr;

   309   register int invalue;

   310   register JDIMENSION colctr;

   311   int inrow;

   312 

   313   for (inrow = 0; inrow < cinfo->max_v_samp_factor; inrow++) {

   314     inptr = input_data[inrow];

   315     outptr = output_data[inrow];

   316     /* Special case for first column */

   317     invalue = GETJSAMPLE(*inptr++);

   318     *outptr++ = (JSAMPLE) invalue;

   319     *outptr++ = (JSAMPLE) ((invalue * 3 + GETJSAMPLE(*inptr) + 2) >> 2);

   320 

   321     for (colctr = compptr->downsampled_width - 2; colctr > 0; colctr--) {

   322       /* General case: 3/4 * nearer pixel + 1/4 * further pixel */

   323       invalue = GETJSAMPLE(*inptr++) * 3;

   324       *outptr++ = (JSAMPLE) ((invalue + GETJSAMPLE(inptr[-2]) + 1) >> 2);

   325       *outptr++ = (JSAMPLE) ((invalue + GETJSAMPLE(*inptr) + 2) >> 2);

   326     }

   327 

   328     /* Special case for last column */

   329     invalue = GETJSAMPLE(*inptr);

   330     *outptr++ = (JSAMPLE) ((invalue * 3 + GETJSAMPLE(inptr[-1]) + 1) >> 2);

   331     *outptr++ = (JSAMPLE) invalue;

   332   }

   333 }

   334 

   335 

   336 /*

   337  * Fancy processing for the common case of 2:1 horizontal and 2:1 vertical.

   338  * Again a triangle filter; see comments for h2v1 case, above.

   339  *

   340  * It is OK for us to reference the adjacent input rows because we demanded

   341  * context from the main buffer controller (see initialization code).

   342  */

   343 

   344 METHODDEF(void)

   345 h2v2_fancy_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,

   346 		     JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)

   347 {

   348   JSAMPARRAY output_data = *output_data_ptr;

   349   register JSAMPROW inptr0, inptr1, outptr;

   350 #if BITS_IN_JSAMPLE == 8

   351   register int thiscolsum, lastcolsum, nextcolsum;

   352 #else

   353   register INT32 thiscolsum, lastcolsum, nextcolsum;

   354 #endif

   355   register JDIMENSION colctr;

   356   int inrow, outrow, v;

   357 

   358   inrow = outrow = 0;

   359   while (outrow < cinfo->max_v_samp_factor) {

   360     for (v = 0; v < 2; v++) {

   361       /* inptr0 points to nearest input row, inptr1 points to next nearest */

   362       inptr0 = input_data[inrow];

   363       if (v == 0)		/* next nearest is row above */

   364 	inptr1 = input_data[inrow-1];

   365       else			/* next nearest is row below */

   366 	inptr1 = input_data[inrow+1];

   367       outptr = output_data[outrow++];

   368 

   369       /* Special case for first column */

   370       thiscolsum = GETJSAMPLE(*inptr0++) * 3 + GETJSAMPLE(*inptr1++);

   371       nextcolsum = GETJSAMPLE(*inptr0++) * 3 + GETJSAMPLE(*inptr1++);

   372       *outptr++ = (JSAMPLE) ((thiscolsum * 4 + 8) >> 4);

   373       *outptr++ = (JSAMPLE) ((thiscolsum * 3 + nextcolsum + 7) >> 4);

   374       lastcolsum = thiscolsum; thiscolsum = nextcolsum;

   375 

   376       for (colctr = compptr->downsampled_width - 2; colctr > 0; colctr--) {

   377 	/* General case: 3/4 * nearer pixel + 1/4 * further pixel in each */

   378 	/* dimension, thus 9/16, 3/16, 3/16, 1/16 overall */

   379 	nextcolsum = GETJSAMPLE(*inptr0++) * 3 + GETJSAMPLE(*inptr1++);

   380 	*outptr++ = (JSAMPLE) ((thiscolsum * 3 + lastcolsum + 8) >> 4);

   381 	*outptr++ = (JSAMPLE) ((thiscolsum * 3 + nextcolsum + 7) >> 4);

   382 	lastcolsum = thiscolsum; thiscolsum = nextcolsum;

   383       }

   384 

   385       /* Special case for last column */

   386       *outptr++ = (JSAMPLE) ((thiscolsum * 3 + lastcolsum + 8) >> 4);

   387       *outptr++ = (JSAMPLE) ((thiscolsum * 4 + 7) >> 4);

   388     }

   389     inrow++;

   390   }

   391 }

   392 

   393 

   394 /*

   395  * Module initialization routine for upsampling.

   396  */

   397 

   398 GLOBAL(void)

   399 jinit_upsampler (j_decompress_ptr cinfo)

   400 {

   401   my_upsample_ptr upsample;

   402   int ci;

   403   jpeg_component_info * compptr;

   404   boolean need_buffer, do_fancy;

   405   int h_in_group, v_in_group, h_out_group, v_out_group;

   406 

   407   upsample = (my_upsample_ptr)

   408     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,

   409 				SIZEOF(my_upsampler));

   410   cinfo->upsample = (struct jpeg_upsampler *) upsample;

   411   upsample->pub.start_pass = start_pass_upsample;

   412   upsample->pub.upsample = sep_upsample;

   413   upsample->pub.need_context_rows = FALSE; /* until we find out differently */

   414 

   415   if (cinfo->CCIR601_sampling)	/* this isn't supported */

   416     ERREXIT(cinfo, JERR_CCIR601_NOTIMPL);

   417 

   418   /* jdmainct.c doesn't support context rows when min_DCT_scaled_size = 1,

   419    * so don't ask for it.

   420    */

   421   do_fancy = cinfo->do_fancy_upsampling && cinfo->min_DCT_scaled_size > 1;

   422 

   423   /* Verify we can handle the sampling factors, select per-component methods,

   424    * and create storage as needed.

   425    */

   426   for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;

   427        ci++, compptr++) {

   428     /* Compute size of an "input group" after IDCT scaling.  This many samples

   429      * are to be converted to max_h_samp_factor * max_v_samp_factor pixels.

   430      */

   431     h_in_group = (compptr->h_samp_factor * compptr->DCT_scaled_size) /

   432 		 cinfo->min_DCT_scaled_size;

   433     v_in_group = (compptr->v_samp_factor * compptr->DCT_scaled_size) /

   434 		 cinfo->min_DCT_scaled_size;

   435     h_out_group = cinfo->max_h_samp_factor;

   436     v_out_group = cinfo->max_v_samp_factor;

   437     upsample->rowgroup_height[ci] = v_in_group; /* save for use later */

   438     need_buffer = TRUE;

   439     if (! compptr->component_needed) {

   440       /* Don't bother to upsample an uninteresting component. */

   441       upsample->methods[ci] = noop_upsample;

   442       need_buffer = FALSE;

   443     } else if (h_in_group == h_out_group && v_in_group == v_out_group) {

   444       /* Fullsize components can be processed without any work. */

   445       upsample->methods[ci] = fullsize_upsample;

   446       need_buffer = FALSE;

   447     } else if (h_in_group * 2 == h_out_group &&

   448 	       v_in_group == v_out_group) {

   449       /* Special cases for 2h1v upsampling */

   450       if (do_fancy && compptr->downsampled_width > 2)

   451 	upsample->methods[ci] = h2v1_fancy_upsample;

   452       else

   453 	upsample->methods[ci] = h2v1_upsample;

   454     } else if (h_in_group * 2 == h_out_group &&

   455 	       v_in_group * 2 == v_out_group) {

   456       /* Special cases for 2h2v upsampling */

   457       if (do_fancy && compptr->downsampled_width > 2) {

   458 	upsample->methods[ci] = h2v2_fancy_upsample;

   459 	upsample->pub.need_context_rows = TRUE;

   460       } else

   461 	upsample->methods[ci] = h2v2_upsample;

   462     } else if ((h_out_group % h_in_group) == 0 &&

   463 	       (v_out_group % v_in_group) == 0) {

   464       /* Generic integral-factors upsampling method */

   465       upsample->methods[ci] = int_upsample;

   466       upsample->h_expand[ci] = (UINT8) (h_out_group / h_in_group);

   467       upsample->v_expand[ci] = (UINT8) (v_out_group / v_in_group);

   468     } else

   469       ERREXIT(cinfo, JERR_FRACT_SAMPLE_NOTIMPL);

   470     if (need_buffer) {

   471       upsample->color_buf[ci] = (*cinfo->mem->alloc_sarray)

   472 	((j_common_ptr) cinfo, JPOOL_IMAGE,

   473 	 (JDIMENSION) jround_up((long) cinfo->output_width,

   474 				(long) cinfo->max_h_samp_factor),

   475 	 (JDIMENSION) cinfo->max_v_samp_factor);

   476     }

   477   }

   478 }