1 line
5.2 KiB
C
1 line
5.2 KiB
C
/*
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* jcprepct.c
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*
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* Copyright (C) 1994, 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 the compression preprocessing controller.
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* This controller manages the color conversion, downsampling,
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* and edge expansion steps.
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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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/* Private buffer controller object */
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typedef struct {
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struct jpeg_c_prep_controller pub; /* public fields */
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/* Downsampling input buffer. This buffer holds color-converted data
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* until we have enough to do a downsample step.
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*/
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JSAMPARRAY color_buf[MAX_COMPONENTS];
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int rows_in_buf; /* counts rows stored in color_buf */
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JDIMENSION rows_to_go; /* counts rows remaining in source image */
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} my_prep_controller;
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typedef my_prep_controller * my_prep_ptr;
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/*
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* Initialize for a processing pass.
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*/
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METHODDEF void
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start_pass (j_compress_ptr cinfo, J_BUF_MODE pass_mode)
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{
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my_prep_ptr prep = (my_prep_ptr) cinfo->prep;
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switch (pass_mode) {
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case JBUF_PASS_THRU:
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break;
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default:
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ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
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break;
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}
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/* Mark the conversion buffer empty */
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prep->rows_in_buf = 0;
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/* Initialize total-height counter for detecting bottom of image */
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prep->rows_to_go = cinfo->image_height;
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}
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/*
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* Expand an image vertically from height input_rows to height output_rows,
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* by duplicating the bottom row.
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*/
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LOCAL void
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expand_bottom_edge (JSAMPARRAY image_data, JDIMENSION num_cols,
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int input_rows, int output_rows)
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{
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register int row;
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for (row = input_rows; row < output_rows; row++) {
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jcopy_sample_rows(image_data, input_rows-1, image_data, row,
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1, num_cols);
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}
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}
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/*
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* Process some data.
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*
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* Preprocessor output data is counted in "row groups". A row group
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* is defined to be v_samp_factor sample rows of each component.
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* Downsampling will produce this much data from each max_v_samp_factor
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* input rows.
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*/
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METHODDEF void
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pre_process_data (j_compress_ptr cinfo,
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JSAMPARRAY input_buf, JDIMENSION *in_row_ctr,
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JDIMENSION in_rows_avail,
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JSAMPIMAGE output_buf, JDIMENSION *out_row_group_ctr,
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JDIMENSION out_row_groups_avail)
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{
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my_prep_ptr prep = (my_prep_ptr) cinfo->prep;
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int numrows, ci;
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JDIMENSION inrows;
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jpeg_component_info * compptr;
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while (*in_row_ctr < in_rows_avail &&
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*out_row_group_ctr < out_row_groups_avail) {
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/* Do color conversion to fill the conversion buffer. */
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inrows = in_rows_avail - *in_row_ctr;
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numrows = cinfo->max_v_samp_factor - prep->rows_in_buf;
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numrows = (int) MIN((JDIMENSION) numrows, inrows);
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(*cinfo->cconvert->color_convert) (cinfo, input_buf + *in_row_ctr,
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prep->color_buf,
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(JDIMENSION) prep->rows_in_buf,
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numrows);
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*in_row_ctr += numrows;
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prep->rows_in_buf += numrows;
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prep->rows_to_go -= numrows;
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/* If at bottom of image, pad to fill the conversion buffer. */
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if (prep->rows_to_go == 0 &&
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prep->rows_in_buf < cinfo->max_v_samp_factor) {
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for (ci = 0; ci < cinfo->num_components; ci++) {
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expand_bottom_edge(prep->color_buf[ci], cinfo->image_width,
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prep->rows_in_buf, cinfo->max_v_samp_factor);
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}
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prep->rows_in_buf = cinfo->max_v_samp_factor;
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}
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/* If we've filled the conversion buffer, empty it. */
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if (prep->rows_in_buf == cinfo->max_v_samp_factor) {
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(*cinfo->downsample->downsample) (cinfo, prep->color_buf,
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output_buf, *out_row_group_ctr);
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prep->rows_in_buf = 0;
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(*out_row_group_ctr)++;
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}
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/* If at bottom of image, pad the output to a full MCU height.
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* Note we assume the caller is providing a one-MCU-height output buffer!
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*/
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if (prep->rows_to_go == 0 &&
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*out_row_group_ctr < out_row_groups_avail) {
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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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expand_bottom_edge(output_buf[ci],
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compptr->width_in_blocks * DCTSIZE,
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(int) (*out_row_group_ctr * compptr->v_samp_factor),
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(int) (out_row_groups_avail * compptr->v_samp_factor));
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}
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*out_row_group_ctr = out_row_groups_avail;
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break; /* can exit outer loop without test */
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}
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}
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}
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/*
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* Initialize preprocessing controller.
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*/
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GLOBAL void
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jinit_c_prep_controller (j_compress_ptr cinfo, boolean need_full_buffer)
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{
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my_prep_ptr prep;
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int ci;
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jpeg_component_info * compptr;
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prep = (my_prep_ptr)
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(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
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SIZEOF(my_prep_controller));
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cinfo->prep = (struct jpeg_c_prep_controller *) prep;
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prep->pub.start_pass = start_pass;
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prep->pub.pre_process_data = pre_process_data;
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/* Allocate the color conversion buffer.
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* We allocate enough storage to allow downsampler to edge-expand in this
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* buffer, if it so chooses.
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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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prep->color_buf[ci] = (*cinfo->mem->alloc_sarray)
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((j_common_ptr) cinfo, JPOOL_IMAGE,
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(JDIMENSION) (((long) compptr->width_in_blocks * DCTSIZE *
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cinfo->max_h_samp_factor) / compptr->h_samp_factor),
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(JDIMENSION) cinfo->max_v_samp_factor);
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}
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}
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