ref: c76cc12a1799ce214b07882eb6f4ab0906c0151b
dir: /sys/src/cmd/gs/jpeg/jdtrans.c/
/* * jdtrans.c * * Copyright (C) 1995-1997, Thomas G. Lane. * 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 library routines for transcoding decompression, * that is, reading raw DCT coefficient arrays from an input JPEG file. * The routines in jdapimin.c will also be needed by a transcoder. */ #define JPEG_INTERNALS #include "jinclude.h" #include "jpeglib.h" /* Forward declarations */ LOCAL(void) transdecode_master_selection JPP((j_decompress_ptr cinfo)); /* * Read the coefficient arrays from a JPEG file. * jpeg_read_header must be completed before calling this. * * The entire image is read into a set of virtual coefficient-block arrays, * one per component. The return value is a pointer to the array of * virtual-array descriptors. These can be manipulated directly via the * JPEG memory manager, or handed off to jpeg_write_coefficients(). * To release the memory occupied by the virtual arrays, call * jpeg_finish_decompress() when done with the data. * * An alternative usage is to simply obtain access to the coefficient arrays * during a buffered-image-mode decompression operation. This is allowed * after any jpeg_finish_output() call. The arrays can be accessed until * jpeg_finish_decompress() is called. (Note that any call to the library * may reposition the arrays, so don't rely on access_virt_barray() results * to stay valid across library calls.) * * Returns NULL if suspended. This case need be checked only if * a suspending data source is used. */ GLOBAL(jvirt_barray_ptr *) jpeg_read_coefficients (j_decompress_ptr cinfo) { if (cinfo->global_state == DSTATE_READY) { /* First call: initialize active modules */ transdecode_master_selection(cinfo); cinfo->global_state = DSTATE_RDCOEFS; } if (cinfo->global_state == DSTATE_RDCOEFS) { /* Absorb whole file into the coef buffer */ for (;;) { int retcode; /* Call progress monitor hook if present */ if (cinfo->progress != NULL) (*cinfo->progress->progress_monitor) ((j_common_ptr) cinfo); /* Absorb some more input */ retcode = (*cinfo->inputctl->consume_input) (cinfo); if (retcode == JPEG_SUSPENDED) return NULL; if (retcode == JPEG_REACHED_EOI) break; /* Advance progress counter if appropriate */ if (cinfo->progress != NULL && (retcode == JPEG_ROW_COMPLETED || retcode == JPEG_REACHED_SOS)) { if (++cinfo->progress->pass_counter >= cinfo->progress->pass_limit) { /* startup underestimated number of scans; ratchet up one scan */ cinfo->progress->pass_limit += (long) cinfo->total_iMCU_rows; } } } /* Set state so that jpeg_finish_decompress does the right thing */ cinfo->global_state = DSTATE_STOPPING; } /* At this point we should be in state DSTATE_STOPPING if being used * standalone, or in state DSTATE_BUFIMAGE if being invoked to get access * to the coefficients during a full buffered-image-mode decompression. */ if ((cinfo->global_state == DSTATE_STOPPING || cinfo->global_state == DSTATE_BUFIMAGE) && cinfo->buffered_image) { return cinfo->coef->coef_arrays; } /* Oops, improper usage */ ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state); return NULL; /* keep compiler happy */ } /* * Master selection of decompression modules for transcoding. * This substitutes for jdmaster.c's initialization of the full decompressor. */ LOCAL(void) transdecode_master_selection (j_decompress_ptr cinfo) { /* This is effectively a buffered-image operation. */ cinfo->buffered_image = TRUE; /* Entropy decoding: either Huffman or arithmetic coding. */ if (cinfo->arith_code) { ERREXIT(cinfo, JERR_ARITH_NOTIMPL); } else { if (cinfo->progressive_mode) { #ifdef D_PROGRESSIVE_SUPPORTED jinit_phuff_decoder(cinfo); #else ERREXIT(cinfo, JERR_NOT_COMPILED); #endif } else jinit_huff_decoder(cinfo); } /* Always get a full-image coefficient buffer. */ jinit_d_coef_controller(cinfo, TRUE); /* We can now tell the memory manager to allocate virtual arrays. */ (*cinfo->mem->realize_virt_arrays) ((j_common_ptr) cinfo); /* Initialize input side of decompressor to consume first scan. */ (*cinfo->inputctl->start_input_pass) (cinfo); /* Initialize progress monitoring. */ if (cinfo->progress != NULL) { int nscans; /* Estimate number of scans to set pass_limit. */ if (cinfo->progressive_mode) { /* Arbitrarily estimate 2 interleaved DC scans + 3 AC scans/component. */ nscans = 2 + 3 * cinfo->num_components; } else if (cinfo->inputctl->has_multiple_scans) { /* For a nonprogressive multiscan file, estimate 1 scan per component. */ nscans = cinfo->num_components; } else { nscans = 1; } cinfo->progress->pass_counter = 0L; cinfo->progress->pass_limit = (long) cinfo->total_iMCU_rows * nscans; cinfo->progress->completed_passes = 0; cinfo->progress->total_passes = 1; } }