nuclear@14: /*
nuclear@14:  * jdtrans.c
nuclear@14:  *
nuclear@14:  * Copyright (C) 1995-1997, Thomas G. Lane.
nuclear@14:  * This file is part of the Independent JPEG Group's software.
nuclear@14:  * For conditions of distribution and use, see the accompanying README file.
nuclear@14:  *
nuclear@14:  * This file contains library routines for transcoding decompression,
nuclear@14:  * that is, reading raw DCT coefficient arrays from an input JPEG file.
nuclear@14:  * The routines in jdapimin.c will also be needed by a transcoder.
nuclear@14:  */
nuclear@14: 
nuclear@14: #define JPEG_INTERNALS
nuclear@14: #include "jinclude.h"
nuclear@14: #include "jpeglib.h"
nuclear@14: 
nuclear@14: 
nuclear@14: /* Forward declarations */
nuclear@14: LOCAL(void) transdecode_master_selection JPP((j_decompress_ptr cinfo));
nuclear@14: 
nuclear@14: 
nuclear@14: /*
nuclear@14:  * Read the coefficient arrays from a JPEG file.
nuclear@14:  * jpeg_read_header must be completed before calling this.
nuclear@14:  *
nuclear@14:  * The entire image is read into a set of virtual coefficient-block arrays,
nuclear@14:  * one per component.  The return value is a pointer to the array of
nuclear@14:  * virtual-array descriptors.  These can be manipulated directly via the
nuclear@14:  * JPEG memory manager, or handed off to jpeg_write_coefficients().
nuclear@14:  * To release the memory occupied by the virtual arrays, call
nuclear@14:  * jpeg_finish_decompress() when done with the data.
nuclear@14:  *
nuclear@14:  * An alternative usage is to simply obtain access to the coefficient arrays
nuclear@14:  * during a buffered-image-mode decompression operation.  This is allowed
nuclear@14:  * after any jpeg_finish_output() call.  The arrays can be accessed until
nuclear@14:  * jpeg_finish_decompress() is called.  (Note that any call to the library
nuclear@14:  * may reposition the arrays, so don't rely on access_virt_barray() results
nuclear@14:  * to stay valid across library calls.)
nuclear@14:  *
nuclear@14:  * Returns NULL if suspended.  This case need be checked only if
nuclear@14:  * a suspending data source is used.
nuclear@14:  */
nuclear@14: 
nuclear@14: GLOBAL(jvirt_barray_ptr *)
nuclear@14: jpeg_read_coefficients (j_decompress_ptr cinfo)
nuclear@14: {
nuclear@14:   if (cinfo->global_state == DSTATE_READY) {
nuclear@14:     /* First call: initialize active modules */
nuclear@14:     transdecode_master_selection(cinfo);
nuclear@14:     cinfo->global_state = DSTATE_RDCOEFS;
nuclear@14:   }
nuclear@14:   if (cinfo->global_state == DSTATE_RDCOEFS) {
nuclear@14:     /* Absorb whole file into the coef buffer */
nuclear@14:     for (;;) {
nuclear@14:       int retcode;
nuclear@14:       /* Call progress monitor hook if present */
nuclear@14:       if (cinfo->progress != NULL)
nuclear@14: 	(*cinfo->progress->progress_monitor) ((j_common_ptr) cinfo);
nuclear@14:       /* Absorb some more input */
nuclear@14:       retcode = (*cinfo->inputctl->consume_input) (cinfo);
nuclear@14:       if (retcode == JPEG_SUSPENDED)
nuclear@14: 	return NULL;
nuclear@14:       if (retcode == JPEG_REACHED_EOI)
nuclear@14: 	break;
nuclear@14:       /* Advance progress counter if appropriate */
nuclear@14:       if (cinfo->progress != NULL &&
nuclear@14: 	  (retcode == JPEG_ROW_COMPLETED || retcode == JPEG_REACHED_SOS)) {
nuclear@14: 	if (++cinfo->progress->pass_counter >= cinfo->progress->pass_limit) {
nuclear@14: 	  /* startup underestimated number of scans; ratchet up one scan */
nuclear@14: 	  cinfo->progress->pass_limit += (long) cinfo->total_iMCU_rows;
nuclear@14: 	}
nuclear@14:       }
nuclear@14:     }
nuclear@14:     /* Set state so that jpeg_finish_decompress does the right thing */
nuclear@14:     cinfo->global_state = DSTATE_STOPPING;
nuclear@14:   }
nuclear@14:   /* At this point we should be in state DSTATE_STOPPING if being used
nuclear@14:    * standalone, or in state DSTATE_BUFIMAGE if being invoked to get access
nuclear@14:    * to the coefficients during a full buffered-image-mode decompression.
nuclear@14:    */
nuclear@14:   if ((cinfo->global_state == DSTATE_STOPPING ||
nuclear@14:        cinfo->global_state == DSTATE_BUFIMAGE) && cinfo->buffered_image) {
nuclear@14:     return cinfo->coef->coef_arrays;
nuclear@14:   }
nuclear@14:   /* Oops, improper usage */
nuclear@14:   ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
nuclear@14:   return NULL;			/* keep compiler happy */
nuclear@14: }
nuclear@14: 
nuclear@14: 
nuclear@14: /*
nuclear@14:  * Master selection of decompression modules for transcoding.
nuclear@14:  * This substitutes for jdmaster.c's initialization of the full decompressor.
nuclear@14:  */
nuclear@14: 
nuclear@14: LOCAL(void)
nuclear@14: transdecode_master_selection (j_decompress_ptr cinfo)
nuclear@14: {
nuclear@14:   /* This is effectively a buffered-image operation. */
nuclear@14:   cinfo->buffered_image = TRUE;
nuclear@14: 
nuclear@14:   /* Entropy decoding: either Huffman or arithmetic coding. */
nuclear@14:   if (cinfo->arith_code) {
nuclear@14:     ERREXIT(cinfo, JERR_ARITH_NOTIMPL);
nuclear@14:   } else {
nuclear@14:     if (cinfo->progressive_mode) {
nuclear@14: #ifdef D_PROGRESSIVE_SUPPORTED
nuclear@14:       jinit_phuff_decoder(cinfo);
nuclear@14: #else
nuclear@14:       ERREXIT(cinfo, JERR_NOT_COMPILED);
nuclear@14: #endif
nuclear@14:     } else
nuclear@14:       jinit_huff_decoder(cinfo);
nuclear@14:   }
nuclear@14: 
nuclear@14:   /* Always get a full-image coefficient buffer. */
nuclear@14:   jinit_d_coef_controller(cinfo, TRUE);
nuclear@14: 
nuclear@14:   /* We can now tell the memory manager to allocate virtual arrays. */
nuclear@14:   (*cinfo->mem->realize_virt_arrays) ((j_common_ptr) cinfo);
nuclear@14: 
nuclear@14:   /* Initialize input side of decompressor to consume first scan. */
nuclear@14:   (*cinfo->inputctl->start_input_pass) (cinfo);
nuclear@14: 
nuclear@14:   /* Initialize progress monitoring. */
nuclear@14:   if (cinfo->progress != NULL) {
nuclear@14:     int nscans;
nuclear@14:     /* Estimate number of scans to set pass_limit. */
nuclear@14:     if (cinfo->progressive_mode) {
nuclear@14:       /* Arbitrarily estimate 2 interleaved DC scans + 3 AC scans/component. */
nuclear@14:       nscans = 2 + 3 * cinfo->num_components;
nuclear@14:     } else if (cinfo->inputctl->has_multiple_scans) {
nuclear@14:       /* For a nonprogressive multiscan file, estimate 1 scan per component. */
nuclear@14:       nscans = cinfo->num_components;
nuclear@14:     } else {
nuclear@14:       nscans = 1;
nuclear@14:     }
nuclear@14:     cinfo->progress->pass_counter = 0L;
nuclear@14:     cinfo->progress->pass_limit = (long) cinfo->total_iMCU_rows * nscans;
nuclear@14:     cinfo->progress->completed_passes = 0;
nuclear@14:     cinfo->progress->total_passes = 1;
nuclear@14:   }
nuclear@14: }