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 /*

  * jcsample.c

  *

  * Copyright (C) 1991-1996, Thomas G. Lane.

  * Copyright 2009 Pierre Ossman <ossman@cendio.se> for Cendio AB

  * 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 downsampling routines.

  *

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

  * is defined to be max_v_samp_factor pixel rows of each component,

  * from which the downsampler produces v_samp_factor sample rows.

  * A single row group is processed in each call to the downsampler module.

  *

  * The downsampler is responsible for edge-expansion of its output data

  * to fill an integral number of DCT blocks horizontally.  The source buffer

  * may be modified if it is helpful for this purpose (the source buffer is

  * allocated wide enough to correspond to the desired output width).

  * The caller (the prep controller) is responsible for vertical padding.

  *

  * The downsampler may request "context rows" by setting need_context_rows

  * during startup.  In this case, the input arrays will contain at least

  * one row group's worth of pixels above and below the passed-in data;

  * the caller will create dummy rows at image top and bottom by replicating

  * the first or last real pixel row.

  *

  * An excellent reference for image resampling is

  *   Digital Image Warping, George Wolberg, 1990.

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

  *

  * The downsampling algorithm used here is a simple average of the source

  * pixels covered by the output pixel.  The hi-falutin sampling literature

  * refers to this as a "box filter".  In general the characteristics of a box

  * filter are not very good, but for the specific cases we normally use (1:1

  * and 2:1 ratios) the box is equivalent to a "triangle filter" which is not

  * nearly so bad.  If you intend to use other sampling ratios, you'd be well

  * advised to improve this code.

  *

  * A simple input-smoothing capability is provided.  This is mainly intended

  * for cleaning up color-dithered GIF input files (if you find it inadequate,

  * we suggest using an external filtering program such as pnmconvol).  When

  * enabled, each input pixel P is replaced by a weighted sum of itself and its

  * eight neighbors.  P's weight is 1-8*SF and each neighbor's weight is SF,

  * where SF = (smoothing_factor / 1024).

  * Currently, smoothing is only supported for 2h2v sampling factors.

  */

 #define JPEG_INTERNALS

 #include "jinclude.h"

 #include "jpeglib.h"

 #include "jsimd.h"

 /* Pointer to routine to downsample a single component */

 typedef JMETHOD(void, downsample1_ptr,

 		(j_compress_ptr cinfo, jpeg_component_info * compptr,

 		 JSAMPARRAY input_data, JSAMPARRAY output_data));

 /* Private subobject */

 typedef struct {

   struct jpeg_downsampler pub;	/* public fields */

   /* Downsampling method pointers, one per component */

   downsample1_ptr methods[MAX_COMPONENTS];

 } my_downsampler;

 typedef my_downsampler * my_downsample_ptr;

 /*

  * Initialize for a downsampling pass.

  */

 METHODDEF(void)

 start_pass_downsample (j_compress_ptr cinfo)

 {

   /* no work for now */

 }

 /*

  * Expand a component horizontally from width input_cols to width output_cols,

  * by duplicating the rightmost samples.

  */

 LOCAL(void)

 expand_right_edge (JSAMPARRAY image_data, int num_rows,

 		   JDIMENSION input_cols, JDIMENSION output_cols)

 {

   register JSAMPROW ptr;

   register JSAMPLE pixval;

   register int count;

   int row;

   int numcols = (int) (output_cols - input_cols);

   if (numcols > 0) {

     for (row = 0; row < num_rows; row++) {

       ptr = image_data[row] + input_cols;

       pixval = ptr[-1];		/* don't need GETJSAMPLE() here */

       for (count = numcols; count > 0; count--)

 	*ptr++ = pixval;

     }

   }

 }

 /*

  * Do downsampling for a whole row group (all components).

  *

  * In this version we simply downsample each component independently.

  */

 METHODDEF(void)

 sep_downsample (j_compress_ptr cinfo,

 		JSAMPIMAGE input_buf, JDIMENSION in_row_index,

 		JSAMPIMAGE output_buf, JDIMENSION out_row_group_index)

 {

   my_downsample_ptr downsample = (my_downsample_ptr) cinfo->downsample;

   int ci;

   jpeg_component_info * compptr;

   JSAMPARRAY in_ptr, out_ptr;

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

        ci++, compptr++) {

     in_ptr = input_buf[ci] + in_row_index;

     out_ptr = output_buf[ci] + (out_row_group_index * compptr->v_samp_factor);

     (*downsample->methods[ci]) (cinfo, compptr, in_ptr, out_ptr);

   }

 }

 /*

  * Downsample pixel values of a single component.

  * One row group is processed per call.

  * This version handles arbitrary integral sampling ratios, without smoothing.

  * Note that this version is not actually used for customary sampling ratios.

  */

 METHODDEF(void)

 int_downsample (j_compress_ptr cinfo, jpeg_component_info * compptr,

 		JSAMPARRAY input_data, JSAMPARRAY output_data)

 {

   int inrow, outrow, h_expand, v_expand, numpix, numpix2, h, v;

   JDIMENSION outcol, outcol_h;	/* outcol_h == outcol*h_expand */

   JDIMENSION output_cols = compptr->width_in_blocks * DCTSIZE;

   JSAMPROW inptr, outptr;

   INT32 outvalue;

   h_expand = cinfo->max_h_samp_factor / compptr->h_samp_factor;

   v_expand = cinfo->max_v_samp_factor / compptr->v_samp_factor;

   numpix = h_expand * v_expand;

   numpix2 = numpix/2;

   /* Expand input data enough to let all the output samples be generated

    * by the standard loop.  Special-casing padded output would be more

    * efficient.

    */

   expand_right_edge(input_data, cinfo->max_v_samp_factor,

 		    cinfo->image_width, output_cols * h_expand);

   inrow = 0;

   for (outrow = 0; outrow < compptr->v_samp_factor; outrow++) {

     outptr = output_data[outrow];

     for (outcol = 0, outcol_h = 0; outcol < output_cols;

 	 outcol++, outcol_h += h_expand) {

       outvalue = 0;

       for (v = 0; v < v_expand; v++) {

 	inptr = input_data[inrow+v] + outcol_h;

 	for (h = 0; h < h_expand; h++) {

 	  outvalue += (INT32) GETJSAMPLE(*inptr++);

 	}

       }

       *outptr++ = (JSAMPLE) ((outvalue + numpix2) / numpix);

     }

     inrow += v_expand;

   }

 }

 /*

  * Downsample pixel values of a single component.

  * This version handles the special case of a full-size component,

  * without smoothing.

  */

 METHODDEF(void)

 fullsize_downsample (j_compress_ptr cinfo, jpeg_component_info * compptr,

 		     JSAMPARRAY input_data, JSAMPARRAY output_data)

 {

   /* Copy the data */

   jcopy_sample_rows(input_data, 0, output_data, 0,

 		    cinfo->max_v_samp_factor, cinfo->image_width);

   /* Edge-expand */

   expand_right_edge(output_data, cinfo->max_v_samp_factor,

 		    cinfo->image_width, compptr->width_in_blocks * DCTSIZE);

 }

 /*

  * Downsample pixel values of a single component.

  * This version handles the common case of 2:1 horizontal and 1:1 vertical,

  * without smoothing.

  *

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

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

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

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

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

  */

 METHODDEF(void)

 h2v1_downsample (j_compress_ptr cinfo, jpeg_component_info * compptr,

 		 JSAMPARRAY input_data, JSAMPARRAY output_data)

 {

   int outrow;

   JDIMENSION outcol;

   JDIMENSION output_cols = compptr->width_in_blocks * DCTSIZE;

   register JSAMPROW inptr, outptr;

   register int bias;

   /* Expand input data enough to let all the output samples be generated

    * by the standard loop.  Special-casing padded output would be more

    * efficient.

    */

   expand_right_edge(input_data, cinfo->max_v_samp_factor,

 		    cinfo->image_width, output_cols * 2);

   for (outrow = 0; outrow < compptr->v_samp_factor; outrow++) {

     outptr = output_data[outrow];

     inptr = input_data[outrow];

     bias = 0;			/* bias = 0,1,0,1,... for successive samples */

     for (outcol = 0; outcol < output_cols; outcol++) {

       *outptr++ = (JSAMPLE) ((GETJSAMPLE(*inptr) + GETJSAMPLE(inptr[1])

 			      + bias) >> 1);

       bias ^= 1;		/* 0=>1, 1=>0 */

       inptr += 2;

     }

   }

 }

 /*

  * Downsample pixel values of a single component.

  * This version handles the standard case of 2:1 horizontal and 2:1 vertical,

  * without smoothing.

  */

 METHODDEF(void)

 h2v2_downsample (j_compress_ptr cinfo, jpeg_component_info * compptr,

 		 JSAMPARRAY input_data, JSAMPARRAY output_data)

 {

   int inrow, outrow;

   JDIMENSION outcol;

   JDIMENSION output_cols = compptr->width_in_blocks * DCTSIZE;

   register JSAMPROW inptr0, inptr1, outptr;

   register int bias;

   /* Expand input data enough to let all the output samples be generated

    * by the standard loop.  Special-casing padded output would be more

    * efficient.

    */

   expand_right_edge(input_data, cinfo->max_v_samp_factor,

 		    cinfo->image_width, output_cols * 2);

   inrow = 0;

   for (outrow = 0; outrow < compptr->v_samp_factor; outrow++) {

     outptr = output_data[outrow];

     inptr0 = input_data[inrow];

     inptr1 = input_data[inrow+1];

     bias = 1;			/* bias = 1,2,1,2,... for successive samples */

     for (outcol = 0; outcol < output_cols; outcol++) {

       *outptr++ = (JSAMPLE) ((GETJSAMPLE(*inptr0) + GETJSAMPLE(inptr0[1]) +

 			      GETJSAMPLE(*inptr1) + GETJSAMPLE(inptr1[1])

 			      + bias) >> 2);

       bias ^= 3;		/* 1=>2, 2=>1 */

       inptr0 += 2; inptr1 += 2;

     }

     inrow += 2;

   }

 }

 #ifdef INPUT_SMOOTHING_SUPPORTED

 /*

  * Downsample pixel values of a single component.

  * This version handles the standard case of 2:1 horizontal and 2:1 vertical,

  * with smoothing.  One row of context is required.

  */

 METHODDEF(void)

 h2v2_smooth_downsample (j_compress_ptr cinfo, jpeg_component_info * compptr,

 			JSAMPARRAY input_data, JSAMPARRAY output_data)

 {

   int inrow, outrow;

   JDIMENSION colctr;

   JDIMENSION output_cols = compptr->width_in_blocks * DCTSIZE;

   register JSAMPROW inptr0, inptr1, above_ptr, below_ptr, outptr;

   INT32 membersum, neighsum, memberscale, neighscale;

   /* Expand input data enough to let all the output samples be generated

    * by the standard loop.  Special-casing padded output would be more

    * efficient.

    */

   expand_right_edge(input_data - 1, cinfo->max_v_samp_factor + 2,

 		    cinfo->image_width, output_cols * 2);

   /* We don't bother to form the individual "smoothed" input pixel values;

    * we can directly compute the output which is the average of the four

    * smoothed values.  Each of the four member pixels contributes a fraction

    * (1-8*SF) to its own smoothed image and a fraction SF to each of the three

    * other smoothed pixels, therefore a total fraction (1-5*SF)/4 to the final

    * output.  The four corner-adjacent neighbor pixels contribute a fraction

    * SF to just one smoothed pixel, or SF/4 to the final output; while the

    * eight edge-adjacent neighbors contribute SF to each of two smoothed

    * pixels, or SF/2 overall.  In order to use integer arithmetic, these

    * factors are scaled by 2^16 = 65536.

    * Also recall that SF = smoothing_factor / 1024.

    */

   memberscale = 16384 - cinfo->smoothing_factor * 80; /* scaled (1-5*SF)/4 */

   neighscale = cinfo->smoothing_factor * 16; /* scaled SF/4 */

   inrow = 0;

   for (outrow = 0; outrow < compptr->v_samp_factor; outrow++) {

     outptr = output_data[outrow];

     inptr0 = input_data[inrow];

     inptr1 = input_data[inrow+1];

     above_ptr = input_data[inrow-1];

     below_ptr = input_data[inrow+2];

     /* Special case for first column: pretend column -1 is same as column 0 */

     membersum = GETJSAMPLE(*inptr0) + GETJSAMPLE(inptr0[1]) +

 		GETJSAMPLE(*inptr1) + GETJSAMPLE(inptr1[1]);

     neighsum = GETJSAMPLE(*above_ptr) + GETJSAMPLE(above_ptr[1]) +

 	       GETJSAMPLE(*below_ptr) + GETJSAMPLE(below_ptr[1]) +

 	       GETJSAMPLE(*inptr0) + GETJSAMPLE(inptr0[2]) +

 	       GETJSAMPLE(*inptr1) + GETJSAMPLE(inptr1[2]);

     neighsum += neighsum;

     neighsum += GETJSAMPLE(*above_ptr) + GETJSAMPLE(above_ptr[2]) +

 		GETJSAMPLE(*below_ptr) + GETJSAMPLE(below_ptr[2]);

     membersum = membersum * memberscale + neighsum * neighscale;

     *outptr++ = (JSAMPLE) ((membersum + 32768) >> 16);

     inptr0 += 2; inptr1 += 2; above_ptr += 2; below_ptr += 2;

     for (colctr = output_cols - 2; colctr > 0; colctr--) {

       /* sum of pixels directly mapped to this output element */

       membersum = GETJSAMPLE(*inptr0) + GETJSAMPLE(inptr0[1]) +

 		  GETJSAMPLE(*inptr1) + GETJSAMPLE(inptr1[1]);

       /* sum of edge-neighbor pixels */

       neighsum = GETJSAMPLE(*above_ptr) + GETJSAMPLE(above_ptr[1]) +

 		 GETJSAMPLE(*below_ptr) + GETJSAMPLE(below_ptr[1]) +

 		 GETJSAMPLE(inptr0[-1]) + GETJSAMPLE(inptr0[2]) +

 		 GETJSAMPLE(inptr1[-1]) + GETJSAMPLE(inptr1[2]);

       /* The edge-neighbors count twice as much as corner-neighbors */

       neighsum += neighsum;

       /* Add in the corner-neighbors */

       neighsum += GETJSAMPLE(above_ptr[-1]) + GETJSAMPLE(above_ptr[2]) +

 		  GETJSAMPLE(below_ptr[-1]) + GETJSAMPLE(below_ptr[2]);

       /* form final output scaled up by 2^16 */

       membersum = membersum * memberscale + neighsum * neighscale;

       /* round, descale and output it */

       *outptr++ = (JSAMPLE) ((membersum + 32768) >> 16);

       inptr0 += 2; inptr1 += 2; above_ptr += 2; below_ptr += 2;

     }

     /* Special case for last column */

     membersum = GETJSAMPLE(*inptr0) + GETJSAMPLE(inptr0[1]) +

 		GETJSAMPLE(*inptr1) + GETJSAMPLE(inptr1[1]);

     neighsum = GETJSAMPLE(*above_ptr) + GETJSAMPLE(above_ptr[1]) +

 	       GETJSAMPLE(*below_ptr) + GETJSAMPLE(below_ptr[1]) +

 	       GETJSAMPLE(inptr0[-1]) + GETJSAMPLE(inptr0[1]) +

 	       GETJSAMPLE(inptr1[-1]) + GETJSAMPLE(inptr1[1]);

     neighsum += neighsum;

     neighsum += GETJSAMPLE(above_ptr[-1]) + GETJSAMPLE(above_ptr[1]) +

 		GETJSAMPLE(below_ptr[-1]) + GETJSAMPLE(below_ptr[1]);

     membersum = membersum * memberscale + neighsum * neighscale;

     *outptr = (JSAMPLE) ((membersum + 32768) >> 16);

     inrow += 2;

   }

 }

 /*

  * Downsample pixel values of a single component.

  * This version handles the special case of a full-size component,

  * with smoothing.  One row of context is required.

  */

 METHODDEF(void)

 fullsize_smooth_downsample (j_compress_ptr cinfo, jpeg_component_info *compptr,

 			    JSAMPARRAY input_data, JSAMPARRAY output_data)

 {

   int outrow;

   JDIMENSION colctr;

   JDIMENSION output_cols = compptr->width_in_blocks * DCTSIZE;

   register JSAMPROW inptr, above_ptr, below_ptr, outptr;

   INT32 membersum, neighsum, memberscale, neighscale;

   int colsum, lastcolsum, nextcolsum;

   /* Expand input data enough to let all the output samples be generated

    * by the standard loop.  Special-casing padded output would be more

    * efficient.

    */

   expand_right_edge(input_data - 1, cinfo->max_v_samp_factor + 2,

 		    cinfo->image_width, output_cols);

   /* Each of the eight neighbor pixels contributes a fraction SF to the

    * smoothed pixel, while the main pixel contributes (1-8*SF).  In order

    * to use integer arithmetic, these factors are multiplied by 2^16 = 65536.

    * Also recall that SF = smoothing_factor / 1024.

    */

   memberscale = 65536L - cinfo->smoothing_factor * 512L; /* scaled 1-8*SF */

   neighscale = cinfo->smoothing_factor * 64; /* scaled SF */

   for (outrow = 0; outrow < compptr->v_samp_factor; outrow++) {

     outptr = output_data[outrow];

     inptr = input_data[outrow];

     above_ptr = input_data[outrow-1];

     below_ptr = input_data[outrow+1];

     /* Special case for first column */

     colsum = GETJSAMPLE(*above_ptr++) + GETJSAMPLE(*below_ptr++) +

 	     GETJSAMPLE(*inptr);

     membersum = GETJSAMPLE(*inptr++);

     nextcolsum = GETJSAMPLE(*above_ptr) + GETJSAMPLE(*below_ptr) +

 		 GETJSAMPLE(*inptr);

     neighsum = colsum + (colsum - membersum) + nextcolsum;

     membersum = membersum * memberscale + neighsum * neighscale;

     *outptr++ = (JSAMPLE) ((membersum + 32768) >> 16);

     lastcolsum = colsum; colsum = nextcolsum;

     for (colctr = output_cols - 2; colctr > 0; colctr--) {

       membersum = GETJSAMPLE(*inptr++);

       above_ptr++; below_ptr++;

       nextcolsum = GETJSAMPLE(*above_ptr) + GETJSAMPLE(*below_ptr) +

 		   GETJSAMPLE(*inptr);

       neighsum = lastcolsum + (colsum - membersum) + nextcolsum;

       membersum = membersum * memberscale + neighsum * neighscale;

       *outptr++ = (JSAMPLE) ((membersum + 32768) >> 16);

       lastcolsum = colsum; colsum = nextcolsum;

     }

     /* Special case for last column */

     membersum = GETJSAMPLE(*inptr);

     neighsum = lastcolsum + (colsum - membersum) + colsum;

     membersum = membersum * memberscale + neighsum * neighscale;

     *outptr = (JSAMPLE) ((membersum + 32768) >> 16);

   }

 }

 #endif /* INPUT_SMOOTHING_SUPPORTED */

 /*

  * Module initialization routine for downsampling.

  * Note that we must select a routine for each component.

  */

 GLOBAL(void)

 jinit_downsampler (j_compress_ptr cinfo)

 {

   my_downsample_ptr downsample;

   int ci;

   jpeg_component_info * compptr;

   boolean smoothok = TRUE;

   downsample = (my_downsample_ptr)

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

 				SIZEOF(my_downsampler));

   cinfo->downsample = (struct jpeg_downsampler *) downsample;

   downsample->pub.start_pass = start_pass_downsample;

   downsample->pub.downsample = sep_downsample;

   downsample->pub.need_context_rows = FALSE;

   if (cinfo->CCIR601_sampling)

     ERREXIT(cinfo, JERR_CCIR601_NOTIMPL);

   /* Verify we can handle the sampling factors, and set up method pointers */

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

        ci++, compptr++) {

     if (compptr->h_samp_factor == cinfo->max_h_samp_factor &&

 	compptr->v_samp_factor == cinfo->max_v_samp_factor) {

 #ifdef INPUT_SMOOTHING_SUPPORTED

       if (cinfo->smoothing_factor) {

 	downsample->methods[ci] = fullsize_smooth_downsample;

 	downsample->pub.need_context_rows = TRUE;

       } else

 #endif

 	downsample->methods[ci] = fullsize_downsample;

     } else if (compptr->h_samp_factor * 2 == cinfo->max_h_samp_factor &&

 	       compptr->v_samp_factor == cinfo->max_v_samp_factor) {

       smoothok = FALSE;

       if (jsimd_can_h2v1_downsample())

         downsample->methods[ci] = jsimd_h2v1_downsample;

       else

         downsample->methods[ci] = h2v1_downsample;

     } else if (compptr->h_samp_factor * 2 == cinfo->max_h_samp_factor &&

 	       compptr->v_samp_factor * 2 == cinfo->max_v_samp_factor) {

 #ifdef INPUT_SMOOTHING_SUPPORTED

       if (cinfo->smoothing_factor) {

 	downsample->methods[ci] = h2v2_smooth_downsample;

 	downsample->pub.need_context_rows = TRUE;

       } else

 #endif

 	if (jsimd_can_h2v2_downsample())

 	  downsample->methods[ci] = jsimd_h2v2_downsample;

 	else

 	  downsample->methods[ci] = h2v2_downsample;

     } else if ((cinfo->max_h_samp_factor % compptr->h_samp_factor) == 0 &&

 	       (cinfo->max_v_samp_factor % compptr->v_samp_factor) == 0) {

       smoothok = FALSE;

       downsample->methods[ci] = int_downsample;

     } else

       ERREXIT(cinfo, JERR_FRACT_SAMPLE_NOTIMPL);

   }

 #ifdef INPUT_SMOOTHING_SUPPORTED

   if (cinfo->smoothing_factor && !smoothok)

     TRACEMS(cinfo, 0, JTRC_SMOOTH_NOTIMPL);

 #endif

 }