jpeg_gen_optimal_table (j_compress_ptr cinfo, JHUFF_TBL * htbl, long freq[])
{
#define MAX_CLEN 32 /* assumed maximum initial code length */
UINT8 bits[MAX_CLEN+1]; /* bits[k] = # of symbols with code length k */
int codesize[257]; /* codesize[k] = code length of symbol k */
int others[257]; /* next symbol in current branch of tree */
int c1, c2;
int p, i, j;
long v;
/* This algorithm is explained in section K.2 of the JPEG standard */
MEMZERO(bits, SIZEOF(bits));
MEMZERO(codesize, SIZEOF(codesize));
for (i = 0; i < 257; i++)
others[i] = -1; /* init links to empty */
freq[256] = 1; /* make sure 256 has a nonzero count */
/* Including the pseudo-symbol 256 in the Huffman procedure guarantees
* that no real symbol is given code-value of all ones, because 256
* will be placed last in the largest codeword category.
*/
/* Huffman's basic algorithm to assign optimal code lengths to symbols */
for (;;) {
/* Find the smallest nonzero frequency, set c1 = its symbol */
/* In case of ties, take the larger symbol number */
c1 = -1;
v = 1000000000L;
for (i = 0; i <= 256; i++) {
if (freq[i] && freq[i] <= v) {
v = freq[i];
c1 = i;
}
}
/* Find the next smallest nonzero frequency, set c2 = its symbol */
/* In case of ties, take the larger symbol number */
c2 = -1;
v = 1000000000L;
for (i = 0; i <= 256; i++) {
if (freq[i] && freq[i] <= v && i != c1) {
v = freq[i];
c2 = i;
}
}
/* Done if we've merged everything into one frequency */
if (c2 < 0)
break;
/* Else merge the two counts/trees */
freq[c1] += freq[c2];
freq[c2] = 0;
/* Increment the codesize of everything in c1's tree branch */
codesize[c1]++;
while (others[c1] >= 0) {
c1 = others[c1];
codesize[c1]++;
}
others[c1] = c2; /* chain c2 onto c1's tree branch */
/* Increment the codesize of everything in c2's tree branch */
codesize[c2]++;
while (others[c2] >= 0) {
c2 = others[c2];
codesize[c2]++;
}
}
/* Now count the number of symbols of each code length */
for (i = 0; i <= 256; i++) {
if (codesize[i]) {
/* The JPEG standard seems to think that this can't happen, */
/* but I'm paranoid... */
if (codesize[i] > MAX_CLEN)
ERREXIT(cinfo, JERR_HUFF_CLEN_OVERFLOW);
bits[codesize[i]]++;
}
}
/* JPEG doesn't allow symbols with code lengths over 16 bits, so if the pure
* Huffman procedure assigned any such lengths, we must adjust the coding.
* Here is what the JPEG spec says about how this next bit works:
* Since symbols are paired for the longest Huffman code, the symbols are
* removed from this length category two at a time. The prefix for the pair
* (which is one bit shorter) is allocated to one of the pair; then,
* skipping the BITS entry for that prefix length, a code word from the next
* shortest nonzero BITS entry is converted into a prefix for two code words
* one bit longer.
*/
for (i = MAX_CLEN; i > 16; i--) {
while (bits[i] > 0) {
j = i - 2; /* find length of new prefix to be used */
while (bits[j] == 0)
j--;
bits[i] -= 2; /* remove two symbols */
bits[i-1]++; /* one goes in this length */
bits[j+1] += 2; /* two new symbols in this length */
bits[j]--; /* symbol of this length is now a prefix */
}
}
/* Remove the count for the pseudo-symbol 256 from the largest codelength */
while (bits[i] == 0) /* find largest codelength still in use */
i--;
bits[i]--;
/* Return final symbol counts (only for lengths 0..16) */
MEMCOPY(htbl->bits, bits, SIZEOF(htbl->bits));
/* Return a list of the symbols sorted by code length */
/* It's not real clear to me why we don't need to consider the codelength
* changes made above, but the JPEG spec seems to think this works.
*/
p = 0;
for (i = 1; i <= MAX_CLEN; i++) {
for (j = 0; j <= 255; j++) {
if (codesize[j] == i) {
htbl->huffval[p] = (UINT8) j;
p++;
}
}
}
/* Set sent_table FALSE so updated table will be written to JPEG file. */
htbl->sent_table = FALSE;
}
jpeg_make_d_derived_tbl (j_decompress_ptr cinfo, boolean isDC, int tblno,
d_derived_tbl ** pdtbl)
{
JHUFF_TBL *htbl;
d_derived_tbl *dtbl;
int p, i, l, si, numsymbols;
int lookbits, ctr;
char huffsize[257];
unsigned int huffcode[257];
unsigned int code;
/* Note that huffsize[] and huffcode[] are filled in code-length order,
* paralleling the order of the symbols themselves in htbl->huffval[].
*/
/* Find the input Huffman table */
if (tblno < 0 || tblno >= NUM_HUFF_TBLS)
ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, tblno);
htbl =
isDC ? cinfo->dc_huff_tbl_ptrs[tblno] : cinfo->ac_huff_tbl_ptrs[tblno];
if (htbl == NULL)
ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, tblno);
/* Allocate a workspace if we haven't already done so. */
if (*pdtbl == NULL)
*pdtbl = (d_derived_tbl *)
(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
SIZEOF(d_derived_tbl));
dtbl = *pdtbl;
dtbl->pub = htbl; /* fill in back link */
/* Figure C.1: make table of Huffman code length for each symbol */
p = 0;
for (l = 1; l <= 16; l++) {
i = (int) htbl->bits[l];
if (i < 0 || p + i > 256) /* protect against table overrun */
ERREXIT(cinfo, JERR_BAD_HUFF_TABLE);
while (i--)
huffsize[p++] = (char) l;
}
huffsize[p] = 0;
numsymbols = p;
/* Figure C.2: generate the codes themselves */
/* We also validate that the counts represent a legal Huffman code tree. */
code = 0;
si = huffsize[0];
p = 0;
while (huffsize[p]) {
while (((int) huffsize[p]) == si) {
huffcode[p++] = code;
code++;
}
/* code is now 1 more than the last code used for codelength si; but
* it must still fit in si bits, since no code is allowed to be all ones.
* BUG FIX: Comparison must be >, not >=
*/
if (((IJG_INT32) code) > (((IJG_INT32) 1) << si))
ERREXIT(cinfo, JERR_BAD_HUFF_TABLE);
code <<= 1;
si++;
}
/* Figure F.15: generate decoding tables for bit-sequential decoding */
p = 0;
for (l = 1; l <= 16; l++) {
if (htbl->bits[l]) {
/* valoffset[l] = huffval[] index of 1st symbol of code length l,
* minus the minimum code of length l
*/
dtbl->valoffset[l] = (IJG_INT32) p - (IJG_INT32) huffcode[p];
p += htbl->bits[l];
dtbl->maxcode[l] = (IJG_INT32)huffcode[p-1]; /* maximum code of length l */
} else {
dtbl->maxcode[l] = -1; /* -1 if no codes of this length */
}
}
dtbl->maxcode[17] = 0xFFFFFL; /* ensures jpeg_huff_decode terminates */
/* Compute lookahead tables to speed up decoding.
* First we set all the table entries to 0, indicating "too long";
* then we iterate through the Huffman codes that are short enough and
* fill in all the entries that correspond to bit sequences starting
* with that code.
*/
MEMZERO(dtbl->look_nbits, SIZEOF(dtbl->look_nbits));
p = 0;
for (l = 1; l <= HUFF_LOOKAHEAD; l++) {
for (i = 1; i <= (int) htbl->bits[l]; i++, p++) {
/* l = current code's length, p = its index in huffcode[] & huffval[]. */
/* Generate left-justified code followed by all possible bit sequences */
lookbits = (int)huffcode[p] << (HUFF_LOOKAHEAD-l);
for (ctr = 1 << (HUFF_LOOKAHEAD-l); ctr > 0; ctr--) {
dtbl->look_nbits[lookbits] = l;
dtbl->look_sym[lookbits] = htbl->huffval[p];
lookbits++;
}
}
}
/* Validate symbols as being reasonable.
* For AC tables, we make no check, but accept all byte values 0..255.
* For DC tables, we require the symbols to be in range 0..16.
* (Tighter bounds could be applied depending on the data depth and mode,
* but this is sufficient to ensure safe decoding.)
*/
if (isDC) {
for (i = 0; i < numsymbols; i++) {
int sym = htbl->huffval[i];
if (sym < 0 || sym > 16)
ERREXIT(cinfo, JERR_BAD_HUFF_TABLE);
}
}
}
start_output_rle (j_decompress_ptr cinfo, djpeg_dest_ptr dinfo)
{
rle_dest_ptr dest = (rle_dest_ptr) dinfo;
size_t cmapsize;
int i, ci;
#ifdef PROGRESS_REPORT
cd_progress_ptr progress = (cd_progress_ptr) cinfo->progress;
#endif
/*
* Make sure the image can be stored in RLE format.
*
* - RLE stores image dimensions as *signed* 16 bit integers. JPEG
* uses unsigned, so we have to check the width.
*
* - Colorspace is expected to be grayscale or RGB.
*
* - The number of channels (components) is expected to be 1 (grayscale/
* pseudocolor) or 3 (truecolor/directcolor).
* (could be 2 or 4 if using an alpha channel, but we aren't)
*/
if (cinfo->output_width > 32767 || cinfo->output_height > 32767)
ERREXIT2(cinfo, JERR_RLE_DIMENSIONS, cinfo->output_width,
cinfo->output_height);
if (cinfo->out_color_space != JCS_GRAYSCALE &&
cinfo->out_color_space != JCS_RGB)
ERREXIT(cinfo, JERR_RLE_COLORSPACE);
if (cinfo->output_components != 1 && cinfo->output_components != 3)
ERREXIT1(cinfo, JERR_RLE_TOOMANYCHANNELS, cinfo->num_components);
/* Convert colormap, if any, to RLE format. */
dest->colormap = NULL;
if (cinfo->quantize_colors) {
/* Allocate storage for RLE-style cmap, zero any extra entries */
cmapsize = cinfo->out_color_components * CMAPLENGTH * SIZEOF(rle_map);
dest->colormap = (rle_map *) (*cinfo->mem->alloc_small)
((j_common_ptr) cinfo, JPOOL_IMAGE, cmapsize);
MEMZERO(dest->colormap, cmapsize);
/* Save away data in RLE format --- note 8-bit left shift! */
/* Shifting would need adjustment for JSAMPLEs wider than 8 bits. */
for (ci = 0; ci < cinfo->out_color_components; ci++) {
for (i = 0; i < cinfo->actual_number_of_colors; i++) {
dest->colormap[ci * CMAPLENGTH + i] =
GETJSAMPLE(cinfo->colormap[ci][i]) << 8;
}
}
}
/* Set the output buffer to the first row */
dest->pub.buffer = (*cinfo->mem->access_virt_sarray)
((j_common_ptr) cinfo, dest->image, (JDIMENSION) 0, (JDIMENSION) 1, TRUE);
dest->pub.buffer_height = 1;
dest->pub.put_pixel_rows = rle_put_pixel_rows;
#ifdef PROGRESS_REPORT
if (progress != NULL) {
progress->total_extra_passes++; /* count file writing as separate pass */
}
#endif
}
start_pass_phuff(j_compress_ptr cinfo, boolean gather_statistics)
{
phuff_entropy_ptr entropy = (phuff_entropy_ptr)cinfo->entropy;
boolean is_DC_band;
int ci, tbl;
jpeg_component_info *compptr;
entropy->cinfo = cinfo;
entropy->gather_statistics = gather_statistics;
is_DC_band = (cinfo->Ss == 0);
/* We assume jcmaster.c already validated the scan parameters. */
/* Select execution routines */
if (cinfo->Ah == 0) {
if (is_DC_band)
entropy->pub.encode_mcu = encode_mcu_DC_first;
else
entropy->pub.encode_mcu = encode_mcu_AC_first;
if (jsimd_can_encode_mcu_AC_first_prepare())
entropy->AC_first_prepare = jsimd_encode_mcu_AC_first_prepare;
else
entropy->AC_first_prepare = encode_mcu_AC_first_prepare;
} else {
if (is_DC_band)
entropy->pub.encode_mcu = encode_mcu_DC_refine;
else {
entropy->pub.encode_mcu = encode_mcu_AC_refine;
if (jsimd_can_encode_mcu_AC_refine_prepare())
entropy->AC_refine_prepare = jsimd_encode_mcu_AC_refine_prepare;
else
entropy->AC_refine_prepare = encode_mcu_AC_refine_prepare;
/* AC refinement needs a correction bit buffer */
if (entropy->bit_buffer == NULL)
entropy->bit_buffer = (char *)
(*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_IMAGE,
MAX_CORR_BITS * sizeof(char));
}
}
if (gather_statistics)
entropy->pub.finish_pass = finish_pass_gather_phuff;
else
entropy->pub.finish_pass = finish_pass_phuff;
/* Only DC coefficients may be interleaved, so cinfo->comps_in_scan = 1
* for AC coefficients.
*/
for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
compptr = cinfo->cur_comp_info[ci];
/* Initialize DC predictions to 0 */
entropy->last_dc_val[ci] = 0;
/* Get table index */
if (is_DC_band) {
if (cinfo->Ah != 0) /* DC refinement needs no table */
continue;
tbl = compptr->dc_tbl_no;
} else {
entropy->ac_tbl_no = tbl = compptr->ac_tbl_no;
}
if (gather_statistics) {
/* Check for invalid table index */
/* (make_c_derived_tbl does this in the other path) */
if (tbl < 0 || tbl >= NUM_HUFF_TBLS)
ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, tbl);
/* Allocate and zero the statistics tables */
/* Note that jpeg_gen_optimal_table expects 257 entries in each table! */
if (entropy->count_ptrs[tbl] == NULL)
entropy->count_ptrs[tbl] = (long *)
(*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_IMAGE,
257 * sizeof(long));
MEMZERO(entropy->count_ptrs[tbl], 257 * sizeof(long));
} else {
/* Compute derived values for Huffman table */
/* We may do this more than once for a table, but it's not expensive */
jpeg_make_c_derived_tbl(cinfo, is_DC_band, tbl,
&entropy->derived_tbls[tbl]);
}
}
/* Initialize AC stuff */
entropy->EOBRUN = 0;
entropy->BE = 0;
/* Initialize bit buffer to empty */
entropy->put_buffer = 0;
entropy->put_bits = 0;
/* Initialize restart stuff */
entropy->restarts_to_go = cinfo->restart_interval;
entropy->next_restart_num = 0;
}
write_bmp_header (j_decompress_ptr cinfo, bmp_dest_ptr dest)
/* Write a Windows-style BMP file header, including colormap if needed */
{
char bmpfileheader[14];
char bmpinfoheader[40];
#define PUT_2B(array,offset,value) \
(array[offset] = (char) ((value) & 0xFF), \
array[offset+1] = (char) (((value) >> 8) & 0xFF))
#define PUT_4B(array,offset,value) \
(array[offset] = (char) ((value) & 0xFF), \
array[offset+1] = (char) (((value) >> 8) & 0xFF), \
array[offset+2] = (char) (((value) >> 16) & 0xFF), \
array[offset+3] = (char) (((value) >> 24) & 0xFF))
INT32 headersize, bfSize;
int bits_per_pixel, cmap_entries;
/* Compute colormap size and total file size */
if (cinfo->out_color_space == JCS_RGB) {
if (cinfo->quantize_colors) {
/* Colormapped RGB */
bits_per_pixel = 8;
cmap_entries = 256;
} else {
/* Unquantized, full color RGB */
bits_per_pixel = 24;
cmap_entries = 0;
}
} else {
/* Grayscale output. We need to fake a 256-entry colormap. */
bits_per_pixel = 8;
cmap_entries = 256;
}
/* File size */
headersize = 14 + 40 + cmap_entries * 4; /* Header and colormap */
bfSize = headersize + (INT32) dest->row_width * (INT32) cinfo->output_height;
/* Set unused fields of header to 0 */
MEMZERO(bmpfileheader, SIZEOF(bmpfileheader));
MEMZERO(bmpinfoheader, SIZEOF(bmpinfoheader));
/* Fill the file header */
bmpfileheader[0] = 0x42; /* first 2 bytes are ASCII 'B', 'M' */
bmpfileheader[1] = 0x4D;
PUT_4B(bmpfileheader, 2, bfSize); /* bfSize */
/* we leave bfReserved1 & bfReserved2 = 0 */
PUT_4B(bmpfileheader, 10, headersize); /* bfOffBits */
/* Fill the info header (Microsoft calls this a BITMAPINFOHEADER) */
PUT_2B(bmpinfoheader, 0, 40); /* biSize */
PUT_4B(bmpinfoheader, 4, cinfo->output_width); /* biWidth */
PUT_4B(bmpinfoheader, 8, cinfo->output_height); /* biHeight */
PUT_2B(bmpinfoheader, 12, 1); /* biPlanes - must be 1 */
PUT_2B(bmpinfoheader, 14, bits_per_pixel); /* biBitCount */
/* we leave biCompression = 0, for none */
/* we leave biSizeImage = 0; this is correct for uncompressed data */
if (cinfo->density_unit == 2) { /* if have density in dots/cm, then */
PUT_4B(bmpinfoheader, 24, (INT32) (cinfo->X_density*100)); /* XPels/M */
PUT_4B(bmpinfoheader, 28, (INT32) (cinfo->Y_density*100)); /* XPels/M */
}
PUT_2B(bmpinfoheader, 32, cmap_entries); /* biClrUsed */
/* we leave biClrImportant = 0 */
if (JFWRITE(dest->pub.output_file, bmpfileheader, 14) != (size_t) 14)
ERREXIT(cinfo, JERR_FILE_WRITE);
if (JFWRITE(dest->pub.output_file, bmpinfoheader, 40) != (size_t) 40)
ERREXIT(cinfo, JERR_FILE_WRITE);
if (cmap_entries > 0)
write_colormap(cinfo, dest, cmap_entries, 4);
}
// algorithm from section K.2 of the JPEG standard
huffman_specification* generate_huffman_specification_table(long freq[])
{
#define MAX_CODE_LEN 32
uint8_t bits[MAX_CODE_LEN + 1]; // bits[k] = # of symbols with code length k
int codesize[257]; // codesize[k] = code length of symbol k
int others[257]; // next symbol in current branch of tree
int v1, v2;
int k, i, j;
long smallest_freq;
MEMZERO(bits);
MEMZERO(codesize);
for (i = 0; i < 257; i++) others[i] = -1; // initialize links to empty
freq[256] = 1; // set the pseudo-symbol 256
// Figure K.1 – Procedure to find Huffman code sizes
while (true)
{
// select the largest value of V with the least value of FREQ(V) greater than zero
v1 = -1;
smallest_freq = 1000000000L;
for (i = 0; i <= 256; i++) {
if (freq[i] && freq[i] <= smallest_freq) {
smallest_freq = freq[i];
v1 = i;
}
}
// Find the next smallest nonzero frequency
v2 = -1;
smallest_freq = 1000000000L;
for (i = 0; i <= 256; i++) {
if (freq[i] && freq[i] <= smallest_freq && i != v1) {
smallest_freq = freq[i];
v2 = i;
}
}
// only one frequency left -> Done
if (v2 < 0)
break;
// merge the two counts
freq[v1] += freq[v2];
freq[v2] = 0;
codesize[v1]++;
while (others[v1] >= 0) {
v1 = others[v1];
codesize[v1]++;
}
others[v1] = v2; // chain v2 onto v1's tree
// Increment the codesize of everything in v2's tree
codesize[v2]++;
while (others[v2] >= 0) {
v2 = others[v2];
codesize[v2]++;
}
}
// Figure K.2 – Procedure to find the number of codes of each size
for (i = 0; i <= 256; i++) {
if (codesize[i]) {
if (codesize[i] > MAX_CODE_LEN) ERREXIT("Huffman code size table overflow");
bits[codesize[i]]++;
}
}
// Figure K.3 – Procedure for limiting code lengths to 16 bits
for (i = MAX_CODE_LEN; i > 16; i--) {
while (bits[i] > 0) {
j = i - 2;
while (bits[j] == 0)
j--;
bits[i] -= 2;
bits[i - 1]++;
bits[j + 1] += 2;
bits[j]--;
}
}
while (bits[i] == 0) //Remove the count for the pseudo-symbol 256 from the largest codelength
i--;
bits[i]--;
huffman_specification* spec = malloc(sizeof(huffman_specification));
MEMZERO(spec->huffval);
memcpy((void *)(spec->bits), (const void *)(bits), (size_t)(sizeof(spec->bits)));
//Figure K.4 – Sorting of input values according to code size
k = 0;
for (i = 1; i <= MAX_CODE_LEN; i++) {
for (j = 0; j <= 255; j++) {
if (codesize[j] == i) {
spec->huffval[k] = (uint8_t)j;
k++;
}
}
}
return spec;
}
