479 lines
16 KiB
C
479 lines
16 KiB
C
/*
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* jdsample.c
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*
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* Copyright (C) 1991-1996, Thomas G. Lane.
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* This file is part of the Independent JPEG Group's software.
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* For conditions of distribution and use, see the accompanying README file.
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*
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* This file contains upsampling routines.
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*
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* Upsampling input data is counted in "row groups". A row group
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* is defined to be (v_samp_factor * DCT_scaled_size / min_DCT_scaled_size)
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* sample rows of each component. Upsampling will normally produce
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* max_v_samp_factor pixel rows from each row group (but this could vary
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* if the upsampler is applying a scale factor of its own).
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*
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* An excellent reference for image resampling is
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* Digital Image Warping, George Wolberg, 1990.
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* Pub. by IEEE Computer Society Press, Los Alamitos, CA. ISBN 0-8186-8944-7.
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*/
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#define JPEG_INTERNALS
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#include "jinclude.h"
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#include "jpeglib.h"
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/* Pointer to routine to upsample a single component */
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typedef JMETHOD(void, upsample1_ptr,
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(j_decompress_ptr cinfo, jpeg_component_info * compptr,
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JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr));
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/* Private subobject */
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typedef struct {
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struct jpeg_upsampler pub; /* public fields */
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/* Color conversion buffer. When using separate upsampling and color
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* conversion steps, this buffer holds one upsampled row group until it
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* has been color converted and output.
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* Note: we do not allocate any storage for component(s) which are full-size,
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* ie do not need rescaling. The corresponding entry of color_buf[] is
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* simply set to point to the input data array, thereby avoiding copying.
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*/
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JSAMPARRAY color_buf[MAX_COMPONENTS];
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/* Per-component upsampling method pointers */
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upsample1_ptr methods[MAX_COMPONENTS];
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int next_row_out; /* counts rows emitted from color_buf */
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JDIMENSION rows_to_go; /* counts rows remaining in image */
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/* Height of an input row group for each component. */
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int rowgroup_height[MAX_COMPONENTS];
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/* These arrays save pixel expansion factors so that int_expand need not
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* recompute them each time. They are unused for other upsampling methods.
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*/
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UINT8 h_expand[MAX_COMPONENTS];
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UINT8 v_expand[MAX_COMPONENTS];
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} my_upsampler;
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typedef my_upsampler * my_upsample_ptr;
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/*
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* Initialize for an upsampling pass.
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*/
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METHODDEF(void)
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start_pass_upsample (j_decompress_ptr cinfo)
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{
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my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
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/* Mark the conversion buffer empty */
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upsample->next_row_out = cinfo->max_v_samp_factor;
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/* Initialize total-height counter for detecting bottom of image */
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upsample->rows_to_go = cinfo->output_height;
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}
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/*
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* Control routine to do upsampling (and color conversion).
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*
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* In this version we upsample each component independently.
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* We upsample one row group into the conversion buffer, then apply
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* color conversion a row at a time.
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*/
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METHODDEF(void)
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sep_upsample (j_decompress_ptr cinfo,
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JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr,
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JDIMENSION in_row_groups_avail,
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JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
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JDIMENSION out_rows_avail)
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{
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my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
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int ci;
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jpeg_component_info * compptr;
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JDIMENSION num_rows;
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/* Fill the conversion buffer, if it's empty */
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if (upsample->next_row_out >= cinfo->max_v_samp_factor) {
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for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
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ci++, compptr++) {
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/* Invoke per-component upsample method. Notice we pass a POINTER
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* to color_buf[ci], so that fullsize_upsample can change it.
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*/
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(*upsample->methods[ci]) (cinfo, compptr,
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input_buf[ci] + (*in_row_group_ctr * upsample->rowgroup_height[ci]),
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upsample->color_buf + ci);
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}
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upsample->next_row_out = 0;
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}
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/* Color-convert and emit rows */
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/* How many we have in the buffer: */
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num_rows = (JDIMENSION) (cinfo->max_v_samp_factor - upsample->next_row_out);
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/* Not more than the distance to the end of the image. Need this test
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* in case the image height is not a multiple of max_v_samp_factor:
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*/
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if (num_rows > upsample->rows_to_go)
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num_rows = upsample->rows_to_go;
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/* And not more than what the client can accept: */
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out_rows_avail -= *out_row_ctr;
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if (num_rows > out_rows_avail)
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num_rows = out_rows_avail;
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(*cinfo->cconvert->color_convert) (cinfo, upsample->color_buf,
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(JDIMENSION) upsample->next_row_out,
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output_buf + *out_row_ctr,
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(int) num_rows);
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/* Adjust counts */
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*out_row_ctr += num_rows;
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upsample->rows_to_go -= num_rows;
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upsample->next_row_out += num_rows;
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/* When the buffer is emptied, declare this input row group consumed */
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if (upsample->next_row_out >= cinfo->max_v_samp_factor)
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(*in_row_group_ctr)++;
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}
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/*
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* These are the routines invoked by sep_upsample to upsample pixel values
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* of a single component. One row group is processed per call.
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*/
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/*
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* For full-size components, we just make color_buf[ci] point at the
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* input buffer, and thus avoid copying any data. Note that this is
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* safe only because sep_upsample doesn't declare the input row group
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* "consumed" until we are done color converting and emitting it.
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*/
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METHODDEF(void)
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fullsize_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,
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JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)
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{
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*output_data_ptr = input_data;
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}
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/*
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* This is a no-op version used for "uninteresting" components.
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* These components will not be referenced by color conversion.
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*/
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METHODDEF(void)
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noop_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,
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JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)
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{
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*output_data_ptr = NULL; /* safety check */
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}
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/*
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* This version handles any integral sampling ratios.
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* This is not used for typical JPEG files, so it need not be fast.
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* Nor, for that matter, is it particularly accurate: the algorithm is
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* simple replication of the input pixel onto the corresponding output
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* pixels. The hi-falutin sampling literature refers to this as a
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* "box filter". A box filter tends to introduce visible artifacts,
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* so if you are actually going to use 3:1 or 4:1 sampling ratios
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* you would be well advised to improve this code.
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*/
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METHODDEF(void)
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int_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,
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JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)
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{
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my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
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JSAMPARRAY output_data = *output_data_ptr;
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register JSAMPROW inptr, outptr;
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register JSAMPLE invalue;
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register int h;
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JSAMPROW outend;
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int h_expand, v_expand;
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int inrow, outrow;
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h_expand = upsample->h_expand[compptr->component_index];
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v_expand = upsample->v_expand[compptr->component_index];
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inrow = outrow = 0;
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while (outrow < cinfo->max_v_samp_factor) {
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/* Generate one output row with proper horizontal expansion */
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inptr = input_data[inrow];
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outptr = output_data[outrow];
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outend = outptr + cinfo->output_width;
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while (outptr < outend) {
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invalue = *inptr++; /* don't need GETJSAMPLE() here */
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for (h = h_expand; h > 0; h--) {
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*outptr++ = invalue;
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}
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}
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/* Generate any additional output rows by duplicating the first one */
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if (v_expand > 1) {
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jcopy_sample_rows(output_data, outrow, output_data, outrow+1,
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v_expand-1, cinfo->output_width);
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}
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inrow++;
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outrow += v_expand;
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}
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}
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/*
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* Fast processing for the common case of 2:1 horizontal and 1:1 vertical.
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* It's still a box filter.
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*/
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METHODDEF(void)
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h2v1_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,
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JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)
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{
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JSAMPARRAY output_data = *output_data_ptr;
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register JSAMPROW inptr, outptr;
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register JSAMPLE invalue;
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JSAMPROW outend;
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int inrow;
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for (inrow = 0; inrow < cinfo->max_v_samp_factor; inrow++) {
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inptr = input_data[inrow];
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outptr = output_data[inrow];
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outend = outptr + cinfo->output_width;
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while (outptr < outend) {
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invalue = *inptr++; /* don't need GETJSAMPLE() here */
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*outptr++ = invalue;
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*outptr++ = invalue;
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}
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}
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}
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/*
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* Fast processing for the common case of 2:1 horizontal and 2:1 vertical.
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* It's still a box filter.
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*/
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METHODDEF(void)
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h2v2_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,
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JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)
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{
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JSAMPARRAY output_data = *output_data_ptr;
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register JSAMPROW inptr, outptr;
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register JSAMPLE invalue;
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JSAMPROW outend;
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int inrow, outrow;
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inrow = outrow = 0;
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while (outrow < cinfo->max_v_samp_factor) {
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inptr = input_data[inrow];
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outptr = output_data[outrow];
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outend = outptr + cinfo->output_width;
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while (outptr < outend) {
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invalue = *inptr++; /* don't need GETJSAMPLE() here */
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*outptr++ = invalue;
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*outptr++ = invalue;
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}
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jcopy_sample_rows(output_data, outrow, output_data, outrow+1,
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1, cinfo->output_width);
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inrow++;
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outrow += 2;
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}
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}
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/*
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* Fancy processing for the common case of 2:1 horizontal and 1:1 vertical.
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*
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* The upsampling algorithm is linear interpolation between pixel centers,
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* also known as a "triangle filter". This is a good compromise between
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* speed and visual quality. The centers of the output pixels are 1/4 and 3/4
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* of the way between input pixel centers.
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*
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* A note about the "bias" calculations: when rounding fractional values to
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* integer, we do not want to always round 0.5 up to the next integer.
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* If we did that, we'd introduce a noticeable bias towards larger values.
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* Instead, this code is arranged so that 0.5 will be rounded up or down at
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* alternate pixel locations (a simple ordered dither pattern).
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*/
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METHODDEF(void)
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h2v1_fancy_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,
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JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)
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{
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JSAMPARRAY output_data = *output_data_ptr;
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register JSAMPROW inptr, outptr;
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register int invalue;
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register JDIMENSION colctr;
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int inrow;
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for (inrow = 0; inrow < cinfo->max_v_samp_factor; inrow++) {
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inptr = input_data[inrow];
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outptr = output_data[inrow];
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/* Special case for first column */
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invalue = GETJSAMPLE(*inptr++);
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*outptr++ = (JSAMPLE) invalue;
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*outptr++ = (JSAMPLE) ((invalue * 3 + GETJSAMPLE(*inptr) + 2) >> 2);
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for (colctr = compptr->downsampled_width - 2; colctr > 0; colctr--) {
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/* General case: 3/4 * nearer pixel + 1/4 * further pixel */
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invalue = GETJSAMPLE(*inptr++) * 3;
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*outptr++ = (JSAMPLE) ((invalue + GETJSAMPLE(inptr[-2]) + 1) >> 2);
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*outptr++ = (JSAMPLE) ((invalue + GETJSAMPLE(*inptr) + 2) >> 2);
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}
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/* Special case for last column */
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invalue = GETJSAMPLE(*inptr);
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*outptr++ = (JSAMPLE) ((invalue * 3 + GETJSAMPLE(inptr[-1]) + 1) >> 2);
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*outptr++ = (JSAMPLE) invalue;
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}
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}
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/*
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* Fancy processing for the common case of 2:1 horizontal and 2:1 vertical.
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* Again a triangle filter; see comments for h2v1 case, above.
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*
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* It is OK for us to reference the adjacent input rows because we demanded
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* context from the main buffer controller (see initialization code).
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*/
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METHODDEF(void)
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h2v2_fancy_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,
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JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)
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{
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JSAMPARRAY output_data = *output_data_ptr;
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register JSAMPROW inptr0, inptr1, outptr;
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#if BITS_IN_JSAMPLE == 8
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register int thiscolsum, lastcolsum, nextcolsum;
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#else
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register INT32 thiscolsum, lastcolsum, nextcolsum;
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#endif
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register JDIMENSION colctr;
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int inrow, outrow, v;
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inrow = outrow = 0;
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while (outrow < cinfo->max_v_samp_factor) {
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for (v = 0; v < 2; v++) {
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/* inptr0 points to nearest input row, inptr1 points to next nearest */
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inptr0 = input_data[inrow];
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if (v == 0) /* next nearest is row above */
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inptr1 = input_data[inrow-1];
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else /* next nearest is row below */
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inptr1 = input_data[inrow+1];
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outptr = output_data[outrow++];
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/* Special case for first column */
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thiscolsum = GETJSAMPLE(*inptr0++) * 3 + GETJSAMPLE(*inptr1++);
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nextcolsum = GETJSAMPLE(*inptr0++) * 3 + GETJSAMPLE(*inptr1++);
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*outptr++ = (JSAMPLE) ((thiscolsum * 4 + 8) >> 4);
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*outptr++ = (JSAMPLE) ((thiscolsum * 3 + nextcolsum + 7) >> 4);
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lastcolsum = thiscolsum; thiscolsum = nextcolsum;
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for (colctr = compptr->downsampled_width - 2; colctr > 0; colctr--) {
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/* General case: 3/4 * nearer pixel + 1/4 * further pixel in each */
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/* dimension, thus 9/16, 3/16, 3/16, 1/16 overall */
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nextcolsum = GETJSAMPLE(*inptr0++) * 3 + GETJSAMPLE(*inptr1++);
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*outptr++ = (JSAMPLE) ((thiscolsum * 3 + lastcolsum + 8) >> 4);
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*outptr++ = (JSAMPLE) ((thiscolsum * 3 + nextcolsum + 7) >> 4);
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lastcolsum = thiscolsum; thiscolsum = nextcolsum;
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}
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/* Special case for last column */
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*outptr++ = (JSAMPLE) ((thiscolsum * 3 + lastcolsum + 8) >> 4);
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*outptr++ = (JSAMPLE) ((thiscolsum * 4 + 7) >> 4);
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}
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inrow++;
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}
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}
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/*
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* Module initialization routine for upsampling.
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*/
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GLOBAL(void)
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jinit_upsampler (j_decompress_ptr cinfo)
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{
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my_upsample_ptr upsample;
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int ci;
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jpeg_component_info * compptr;
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boolean need_buffer, do_fancy;
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int h_in_group, v_in_group, h_out_group, v_out_group;
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upsample = (my_upsample_ptr)
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(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
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SIZEOF(my_upsampler));
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cinfo->upsample = (struct jpeg_upsampler *) upsample;
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upsample->pub.start_pass = start_pass_upsample;
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upsample->pub.upsample = sep_upsample;
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upsample->pub.need_context_rows = FALSE; /* until we find out differently */
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if (cinfo->CCIR601_sampling) /* this isn't supported */
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ERREXIT(cinfo, JERR_CCIR601_NOTIMPL);
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/* jdmainct.c doesn't support context rows when min_DCT_scaled_size = 1,
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* so don't ask for it.
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*/
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do_fancy = cinfo->do_fancy_upsampling && cinfo->min_DCT_scaled_size > 1;
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/* Verify we can handle the sampling factors, select per-component methods,
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* and create storage as needed.
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*/
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for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
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ci++, compptr++) {
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/* Compute size of an "input group" after IDCT scaling. This many samples
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* are to be converted to max_h_samp_factor * max_v_samp_factor pixels.
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*/
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h_in_group = (compptr->h_samp_factor * compptr->DCT_scaled_size) /
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cinfo->min_DCT_scaled_size;
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v_in_group = (compptr->v_samp_factor * compptr->DCT_scaled_size) /
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cinfo->min_DCT_scaled_size;
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h_out_group = cinfo->max_h_samp_factor;
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v_out_group = cinfo->max_v_samp_factor;
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upsample->rowgroup_height[ci] = v_in_group; /* save for use later */
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need_buffer = TRUE;
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if (! compptr->component_needed) {
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/* Don't bother to upsample an uninteresting component. */
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upsample->methods[ci] = noop_upsample;
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need_buffer = FALSE;
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} else if (h_in_group == h_out_group && v_in_group == v_out_group) {
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/* Fullsize components can be processed without any work. */
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upsample->methods[ci] = fullsize_upsample;
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need_buffer = FALSE;
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} else if (h_in_group * 2 == h_out_group &&
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v_in_group == v_out_group) {
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/* Special cases for 2h1v upsampling */
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if (do_fancy && compptr->downsampled_width > 2)
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upsample->methods[ci] = h2v1_fancy_upsample;
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else
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upsample->methods[ci] = h2v1_upsample;
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} else if (h_in_group * 2 == h_out_group &&
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v_in_group * 2 == v_out_group) {
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/* Special cases for 2h2v upsampling */
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if (do_fancy && compptr->downsampled_width > 2) {
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upsample->methods[ci] = h2v2_fancy_upsample;
|
|
upsample->pub.need_context_rows = TRUE;
|
|
} else
|
|
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);
|
|
if (need_buffer) {
|
|
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);
|
|
}
|
|
}
|
|
}
|