| /* |
| * jdtrans.c |
| * |
| * This file was part of the Independent JPEG Group's software: |
| * Copyright (C) 1995-1997, Thomas G. Lane. |
| * libjpeg-turbo Modifications: |
| * Copyright (C) 2020, 2022, D. R. Commander. |
| * For conditions of distribution and use, see the accompanying README.ijg |
| * 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" |
| #include "jpegapicomp.h" |
| |
| |
| /* Forward declarations */ |
| LOCAL(void) transdecode_master_selection(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->master->lossless) |
| ERREXIT(cinfo, JERR_NOTIMPL); |
| |
| 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; |
| |
| #if JPEG_LIB_VERSION >= 80 |
| /* Compute output image dimensions and related values. */ |
| jpeg_core_output_dimensions(cinfo); |
| #endif |
| |
| /* Entropy decoding: either Huffman or arithmetic coding. */ |
| if (cinfo->arith_code) { |
| #ifdef D_ARITH_CODING_SUPPORTED |
| jinit_arith_decoder(cinfo); |
| #else |
| ERREXIT(cinfo, JERR_ARITH_NOTIMPL); |
| #endif |
| } 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. */ |
| if (cinfo->data_precision == 12) |
| j12init_d_coef_controller(cinfo, TRUE); |
| else |
| 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; |
| } |
| } |