    /*
     * jdsample.c
     *
     * Copyright (C) 1991-1996, Thomas G. Lane.
     * Modified 2002-2020 by 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 upsampling routines.
     *
     * Upsampling input data is counted in "row groups".  A row group
     * is defined to be (v_samp_factor * DCT_v_scaled_size / min_DCT_v_scaled_size)
     * sample rows of each component.  Upsampling will normally produce
     * max_v_samp_factor pixel rows from each row group (but this could vary
     * if the upsampler is applying a scale factor of its own).
     *
     * 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.
     */

    #define JPEG_INTERNALS
    #include "jinclude.h"
    #include "jpeglib.h"

    /* Pointer to routine to upsample a single component */
    typedef JMETHOD(void, upsample1_ptr,
    		(j_decompress_ptr cinfo, jpeg_component_info * compptr,
    		 JSAMPARRAY input_data, JSAMPIMAGE output_data_ptr));

    /* Private subobject */

    typedef struct {
      struct jpeg_upsampler pub;	/* public fields */

      /* Color conversion buffer.  When using separate upsampling and color
       * conversion steps, this buffer holds one upsampled row group until it
       * has been color converted and output.
       * Note: we do not allocate any storage for component(s) which are full-size,
       * ie do not need rescaling.  The corresponding entry of color_buf[] is
       * simply set to point to the input data array, thereby avoiding copying.
       */
      JSAMPARRAY color_buf[MAX_COMPONENTS];

      /* Per-component upsampling method pointers */
      upsample1_ptr methods[MAX_COMPONENTS];

      int next_row_out;		/* counts rows emitted from color_buf */
      JDIMENSION rows_to_go;	/* counts rows remaining in image */

      /* Height of an input row group for each component. */
      int rowgroup_height[MAX_COMPONENTS];

      /* These arrays save pixel expansion factors so that int_expand need not
       * recompute them each time.  They are unused for other upsampling methods.
       */
      UINT8 h_expand[MAX_COMPONENTS];
      UINT8 v_expand[MAX_COMPONENTS];
    } my_upsampler;

    typedef my_upsampler * my_upsample_ptr;

    /*
     * Initialize for an upsampling pass.
     */

    METHODDEF(void)
    start_pass_upsample (j_decompress_ptr cinfo)
    {
      my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;

      /* Mark the conversion buffer empty */
      upsample->next_row_out = cinfo->max_v_samp_factor;
      /* Initialize total-height counter for detecting bottom of image */
      upsample->rows_to_go = cinfo->output_height;
    }

    /*
     * Control routine to do upsampling (and color conversion).
     *
     * In this version we upsample each component independently.
     * We upsample one row group into the conversion buffer, then apply
     * color conversion a row at a time.
     */

    METHODDEF(void)
    sep_upsample (j_decompress_ptr cinfo,
    	      JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr,
    	      JDIMENSION in_row_groups_avail,
    	      JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
    	      JDIMENSION out_rows_avail)
    {
      my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
      int ci;
      jpeg_component_info * compptr;
      JDIMENSION num_rows;

      /* Fill the conversion buffer, if it's empty */
      if (upsample->next_row_out >= cinfo->max_v_samp_factor) {
        for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
    	 ci++, compptr++) {
          /* Don't bother to upsample an uninteresting component. */
          if (! compptr->component_needed)
    	continue;
          /* Invoke per-component upsample method.  Notice we pass a POINTER
           * to color_buf[ci], so that fullsize_upsample can change it.
           */
          (*upsample->methods[ci]) (cinfo, compptr,
    	input_buf[ci] + (*in_row_group_ctr * upsample->rowgroup_height[ci]),
    	upsample->color_buf + ci);
        }
        upsample->next_row_out = 0;
      }

      /* Color-convert and emit rows */

      /* How many we have in the buffer: */
      num_rows = (JDIMENSION) (cinfo->max_v_samp_factor - upsample->next_row_out);
      /* Not more than the distance to the end of the image.  Need this test
       * in case the image height is not a multiple of max_v_samp_factor:
       */
      if (num_rows > upsample->rows_to_go)
        num_rows = upsample->rows_to_go;
      /* And not more than what the client can accept: */
      out_rows_avail -= *out_row_ctr;
      if (num_rows > out_rows_avail)
        num_rows = out_rows_avail;

      (*cinfo->cconvert->color_convert) (cinfo, upsample->color_buf,
    				     (JDIMENSION) upsample->next_row_out,
    				     output_buf + *out_row_ctr,
    				     (int) num_rows);

      /* Adjust counts */
      *out_row_ctr += num_rows;
      upsample->rows_to_go -= num_rows;
      upsample->next_row_out += num_rows;
      /* When the buffer is emptied, declare this input row group consumed */
      if (upsample->next_row_out >= cinfo->max_v_samp_factor)
        (*in_row_group_ctr)++;
    }

    /*
     * These are the routines invoked by sep_upsample to upsample pixel values
     * of a single component.  One row group is processed per call.
     */

    /*
     * For full-size components, we just make color_buf[ci] point at the
     * input buffer, and thus avoid copying any data.  Note that this is
     * safe only because sep_upsample doesn't declare the input row group
     * "consumed" until we are done color converting and emitting it.
     */

    METHODDEF(void)
    fullsize_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,
    		   JSAMPARRAY input_data, JSAMPIMAGE output_data_ptr)
    {
      *output_data_ptr = input_data;
    }

    /*
     * This version handles any integral sampling ratios.
     * This is not used for typical JPEG files, so it need not be fast.
     * Nor, for that matter, is it particularly accurate: the algorithm is
     * simple replication of the input pixel onto the corresponding output
     * pixels.  The hi-falutin sampling literature refers to this as a
     * "box filter".  A box filter tends to introduce visible artifacts,
     * so if you are actually going to use 3:1 or 4:1 sampling ratios
     * you would be well advised to improve this code.
     */

    METHODDEF(void)
    int_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,
    	      JSAMPARRAY input_data, JSAMPIMAGE output_data_ptr)
    {
      my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
      JSAMPARRAY output_data, output_end;
      register JSAMPROW inptr, outptr;
      register JSAMPLE invalue;
      register int h;
      JSAMPROW outend;
      int h_expand, v_expand;

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

      output_data = *output_data_ptr;
      output_end = output_data + cinfo->max_v_samp_factor;
      for (; output_data < output_end; output_data += v_expand) {
        /* Generate one output row with proper horizontal expansion */
        inptr = *input_data++;
        outptr = *output_data;
        outend = outptr + cinfo->output_width;
        while (outptr < outend) {
          invalue = *inptr++;	/* don't need GETJSAMPLE() here */
          for (h = h_expand; h > 0; h--) {
    	*outptr++ = invalue;
          }
        }
        /* Generate any additional output rows by duplicating the first one */
        if (v_expand > 1) {
          jcopy_sample_rows(output_data, output_data + 1,
    			v_expand - 1, cinfo->output_width);
        }
      }
    }

    /*
     * Fast processing for the common case of 2:1 horizontal and 1:1 vertical.
     * It's still a box filter.
     */

    METHODDEF(void)
    h2v1_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,
    	       JSAMPARRAY input_data, JSAMPIMAGE output_data_ptr)
    {
      JSAMPARRAY output_data = *output_data_ptr;
      register JSAMPROW inptr, outptr;
      register JSAMPLE invalue;
      JSAMPROW outend;
      int outrow;

      for (outrow = 0; outrow < cinfo->max_v_samp_factor; outrow++) {
        inptr = input_data[outrow];
        outptr = output_data[outrow];
        outend = outptr + cinfo->output_width;
        while (outptr < outend) {
          invalue = *inptr++;	/* don't need GETJSAMPLE() here */
          *outptr++ = invalue;
          *outptr++ = invalue;
        }
      }
    }

    /*
     * Fast processing for the common case of 2:1 horizontal and 2:1 vertical.
     * It's still a box filter.
     */

    METHODDEF(void)
    h2v2_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,
    	       JSAMPARRAY input_data, JSAMPIMAGE output_data_ptr)
    {
      JSAMPARRAY output_data, output_end;
      register JSAMPROW inptr, outptr;
      register JSAMPLE invalue;
      JSAMPROW outend;

      output_data = *output_data_ptr;
      output_end = output_data + cinfo->max_v_samp_factor;
      for (; output_data < output_end; output_data += 2) {
        inptr = *input_data++;
        outptr = *output_data;
        outend = outptr + cinfo->output_width;
        while (outptr < outend) {
          invalue = *inptr++;	/* don't need GETJSAMPLE() here */
          *outptr++ = invalue;
          *outptr++ = invalue;
        }
        jcopy_sample_rows(output_data, output_data + 1,
    		      1, cinfo->output_width);
      }
    }

    /*
     * Module initialization routine for upsampling.
     */

    GLOBAL(void)
    jinit_upsampler (j_decompress_ptr cinfo)
    {
      my_upsample_ptr upsample;
      int ci;
      jpeg_component_info * compptr;
      int h_in_group, v_in_group, h_out_group, v_out_group;

      upsample = (my_upsample_ptr) (*cinfo->mem->alloc_small)
        ((j_common_ptr) cinfo, JPOOL_IMAGE, SIZEOF(my_upsampler));
      cinfo->upsample = &upsample->pub;
      upsample->pub.start_pass = start_pass_upsample;
      upsample->pub.upsample = sep_upsample;
      upsample->pub.need_context_rows = FALSE; /* until we find out differently */

      if (cinfo->CCIR601_sampling)	/* this isn't supported */
        ERREXIT(cinfo, JERR_CCIR601_NOTIMPL);

      /* Verify we can handle the sampling factors, select per-component methods,
       * and create storage as needed.
       */
      for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
           ci++, compptr++) {
        /* Don't bother to upsample an uninteresting component. */
        if (! compptr->component_needed)
          continue;
        /* Compute size of an "input group" after IDCT scaling.  This many samples
         * are to be converted to max_h_samp_factor * max_v_samp_factor pixels.
         */
        h_in_group = (compptr->h_samp_factor * compptr->DCT_h_scaled_size) /
    		 cinfo->min_DCT_h_scaled_size;
        v_in_group = (compptr->v_samp_factor * compptr->DCT_v_scaled_size) /
    		 cinfo->min_DCT_v_scaled_size;
        h_out_group = cinfo->max_h_samp_factor;
        v_out_group = cinfo->max_v_samp_factor;
        upsample->rowgroup_height[ci] = v_in_group; /* save for use later */
        if (h_in_group == h_out_group && v_in_group == v_out_group) {
          /* Fullsize components can be processed without any work. */
          upsample->methods[ci] = fullsize_upsample;
          continue;		/* don't need to allocate buffer */
        }
        if (h_in_group * 2 == h_out_group && v_in_group == v_out_group) {
          /* Special case for 2h1v upsampling */
          upsample->methods[ci] = h2v1_upsample;
        } else if (h_in_group * 2 == h_out_group &&
    	       v_in_group * 2 == v_out_group) {
          /* Special case for 2h2v upsampling */
          upsample->methods[ci] = h2v2_upsample;
        } else if ((h_out_group % h_in_group) == 0 &&
    	       (v_out_group % v_in_group) == 0) {
          /* Generic integral-factors upsampling method */
          upsample->methods[ci] = int_upsample;
          upsample->h_expand[ci] = (UINT8) (h_out_group / h_in_group);
          upsample->v_expand[ci] = (UINT8) (v_out_group / v_in_group);
        } else
          ERREXIT(cinfo, JERR_FRACT_SAMPLE_NOTIMPL);
        upsample->color_buf[ci] = (*cinfo->mem->alloc_sarray)
          ((j_common_ptr) cinfo, JPOOL_IMAGE,
           (JDIMENSION) jround_up((long) cinfo->output_width,
    			      (long) cinfo->max_h_samp_factor),
           (JDIMENSION) cinfo->max_v_samp_factor);
      }
    }