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Pillow/src/libImaging/JpegEncode.c
Benjamin Gilbert 4d7372bfd0 Implement streamtype=1 option for tables-only JPEG encoding 
We already support streamtype=2 to skip producing JPEG tables, but
streamtype=1, which skips everything but the tables, was never implemented.
The streamtype=1 stub code dates to Git pre-history, so it's not
immediately clear why.  Implement the missing support.

jpeg_write_tables() can't resume after a full output buffer (it fails with
JERR_CANT_SUSPEND), so it might seem that Pillow needs to pre-compute the
necessary buffer size.  However, in the normal case of producing an
interchange stream, the tables are written via the same libjpeg codepath
during the first jpeg_write_scanlines() call, and table writes aren't
resumable there either.  Thus, any buffer large enough for the normal case
will also be large enough for a tables-only file.

The streamtype option isn't documented and this commit doesn't change that.
It does add a test though.

Co-authored-by: Andrew Murray <radarhere@users.noreply.github.com>
2023-10-24 20:30:45 -05:00

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/*
* The Python Imaging Library.
* $Id$
*
* coder for JPEG data
*
* history:
* 1996-05-06 fl created
* 1996-07-16 fl don't drop last block of encoded data
* 1996-12-30 fl added quality and progressive settings
* 1997-01-08 fl added streamtype settings
* 1998-01-31 fl adapted to libjpeg 6a
* 1998-07-12 fl added YCbCr support
* 2001-04-16 fl added DPI write support
*
* Copyright (c) 1997-2001 by Secret Labs AB
* Copyright (c) 1995-1997 by Fredrik Lundh
*
* See the README file for details on usage and redistribution.
*/
#include "Imaging.h"
#ifdef HAVE_LIBJPEG
#undef HAVE_PROTOTYPES
#undef HAVE_STDLIB_H
#undef HAVE_STDDEF_H
#undef UINT8
#undef UINT16
#undef UINT32
#undef INT16
#undef INT32
#include "Jpeg.h"
/* -------------------------------------------------------------------- */
/* Suspending output handler */
/* -------------------------------------------------------------------- */
METHODDEF(void)
stub(j_compress_ptr cinfo) { /* empty */ }
METHODDEF(boolean)
empty_output_buffer(j_compress_ptr cinfo) {
/* Suspension */
return FALSE;
}
GLOBAL(void)
jpeg_buffer_dest(j_compress_ptr cinfo, JPEGDESTINATION *destination) {
cinfo->dest = (void *)destination;
destination->pub.init_destination = stub;
destination->pub.empty_output_buffer = empty_output_buffer;
destination->pub.term_destination = stub;
}
/* -------------------------------------------------------------------- */
/* Error handler */
/* -------------------------------------------------------------------- */
METHODDEF(void)
error(j_common_ptr cinfo) {
JPEGERROR *error;
error = (JPEGERROR *)cinfo->err;
(*cinfo->err->output_message)(cinfo);
longjmp(error->setjmp_buffer, 1);
}
/* -------------------------------------------------------------------- */
/* Encoder */
/* -------------------------------------------------------------------- */
int
ImagingJpegEncode(Imaging im, ImagingCodecState state, UINT8 *buf, int bytes) {
JPEGENCODERSTATE *context = (JPEGENCODERSTATE *)state->context;
int ok;
if (setjmp(context->error.setjmp_buffer)) {
/* JPEG error handler */
jpeg_destroy_compress(&context->cinfo);
state->errcode = IMAGING_CODEC_BROKEN;
return -1;
}
if (!state->state) {
/* Setup compression context (very similar to the decoder) */
context->cinfo.err = jpeg_std_error(&context->error.pub);
context->error.pub.error_exit = error;
jpeg_create_compress(&context->cinfo);
jpeg_buffer_dest(&context->cinfo, &context->destination);
context->extra_offset = 0;
/* Ready to encode */
state->state = 1;
}
/* Load the destination buffer */
context->destination.pub.next_output_byte = buf;
context->destination.pub.free_in_buffer = bytes;
switch (state->state) {
case 1:
context->cinfo.image_width = state->xsize;
context->cinfo.image_height = state->ysize;
switch (state->bits) {
case 8:
context->cinfo.input_components = 1;
context->cinfo.in_color_space = JCS_GRAYSCALE;
break;
case 24:
context->cinfo.input_components = 3;
if (strcmp(im->mode, "YCbCr") == 0) {
context->cinfo.in_color_space = JCS_YCbCr;
} else {
context->cinfo.in_color_space = JCS_RGB;
}
break;
case 32:
context->cinfo.input_components = 4;
context->cinfo.in_color_space = JCS_CMYK;
#ifdef JCS_EXTENSIONS
if (strcmp(context->rawmode, "RGBX") == 0) {
context->cinfo.in_color_space = JCS_EXT_RGBX;
}
#endif
break;
default:
state->errcode = IMAGING_CODEC_CONFIG;
return -1;
}
/* Compressor configuration */
jpeg_set_defaults(&context->cinfo);
/* Use custom quantization tables */
if (context->qtables) {
int i;
int quality = 100;
int last_q = 0;
if (context->quality != -1) {
quality = context->quality;
}
for (i = 0; i < context->qtablesLen; i++) {
jpeg_add_quant_table(
&context->cinfo,
i,
&context->qtables[i * DCTSIZE2],
quality,
FALSE);
context->cinfo.comp_info[i].quant_tbl_no = i;
last_q = i;
}
if (context->qtablesLen == 1) {
// jpeg_set_defaults created two qtables internally, but we only
// wanted one.
jpeg_add_quant_table(
&context->cinfo, 1, &context->qtables[0], quality, FALSE);
}
for (i = last_q; i < context->cinfo.num_components; i++) {
context->cinfo.comp_info[i].quant_tbl_no = last_q;
}
} else if (context->quality != -1) {
jpeg_set_quality(&context->cinfo, context->quality, TRUE);
}
/* Set subsampling options */
switch (context->subsampling) {
case 0: /* 1x1 1x1 1x1 (4:4:4) : None */
{
context->cinfo.comp_info[0].h_samp_factor = 1;
context->cinfo.comp_info[0].v_samp_factor = 1;
context->cinfo.comp_info[1].h_samp_factor = 1;
context->cinfo.comp_info[1].v_samp_factor = 1;
context->cinfo.comp_info[2].h_samp_factor = 1;
context->cinfo.comp_info[2].v_samp_factor = 1;
break;
}
case 1: /* 2x1, 1x1, 1x1 (4:2:2) : Medium */
{
context->cinfo.comp_info[0].h_samp_factor = 2;
context->cinfo.comp_info[0].v_samp_factor = 1;
context->cinfo.comp_info[1].h_samp_factor = 1;
context->cinfo.comp_info[1].v_samp_factor = 1;
context->cinfo.comp_info[2].h_samp_factor = 1;
context->cinfo.comp_info[2].v_samp_factor = 1;
break;
}
case 2: /* 2x2, 1x1, 1x1 (4:2:0) : High */
{
context->cinfo.comp_info[0].h_samp_factor = 2;
context->cinfo.comp_info[0].v_samp_factor = 2;
context->cinfo.comp_info[1].h_samp_factor = 1;
context->cinfo.comp_info[1].v_samp_factor = 1;
context->cinfo.comp_info[2].h_samp_factor = 1;
context->cinfo.comp_info[2].v_samp_factor = 1;
break;
}
default: {
/* Use the lib's default */
break;
}
}
if (context->progressive) {
jpeg_simple_progression(&context->cinfo);
}
context->cinfo.smoothing_factor = context->smooth;
context->cinfo.optimize_coding = (boolean)context->optimize;
if (context->xdpi > 0 && context->ydpi > 0) {
context->cinfo.write_JFIF_header = TRUE;
context->cinfo.density_unit = 1; /* dots per inch */
context->cinfo.X_density = context->xdpi;
context->cinfo.Y_density = context->ydpi;
}
switch (context->streamtype) {
case 1:
/* tables only */
jpeg_write_tables(&context->cinfo);
goto cleanup;
case 2:
/* image only */
jpeg_suppress_tables(&context->cinfo, TRUE);
jpeg_start_compress(&context->cinfo, FALSE);
/* suppress extra section */
context->extra_offset = context->extra_size;
break;
default:
/* interchange stream */
jpeg_start_compress(&context->cinfo, TRUE);
break;
}
state->state++;
/* fall through */
case 2:
// check for exif len + 'APP1' header bytes
if (context->rawExifLen + 5 > context->destination.pub.free_in_buffer) {
break;
}
// add exif header
if (context->rawExifLen > 0) {
jpeg_write_marker(
&context->cinfo,
JPEG_APP0 + 1,
(unsigned char *)context->rawExif,
context->rawExifLen);
}
state->state++;
/* fall through */
case 3:
if (context->extra) {
/* copy extra buffer to output buffer */
unsigned int n = context->extra_size - context->extra_offset;
if (n > context->destination.pub.free_in_buffer) {
n = context->destination.pub.free_in_buffer;
}
memcpy(
context->destination.pub.next_output_byte,
context->extra + context->extra_offset,
n);
context->destination.pub.next_output_byte += n;
context->destination.pub.free_in_buffer -= n;
context->extra_offset += n;
if (context->extra_offset >= context->extra_size) {
state->state++;
} else {
break;
}
} else {
state->state++;
}
case 4:
if (context->comment) {
jpeg_write_marker(&context->cinfo, JPEG_COM, (unsigned char *)context->comment, context->comment_size);
}
state->state++;
case 5:
if (1024 > context->destination.pub.free_in_buffer) {
break;
}
ok = 1;
while (state->y < state->ysize) {
state->shuffle(
state->buffer,
(UINT8 *)im->image[state->y + state->yoff] +
state->xoff * im->pixelsize,
state->xsize);
ok = jpeg_write_scanlines(&context->cinfo, &state->buffer, 1);
if (ok != 1) {
break;
}
state->y++;
}
if (ok != 1) {
break;
}
state->state++;
/* fall through */
case 6:
/* Finish compression */
if (context->destination.pub.free_in_buffer < 100) {
break;
}
jpeg_finish_compress(&context->cinfo);
cleanup:
/* Clean up */
if (context->comment) {
free(context->comment);
context->comment = NULL;
}
if (context->extra) {
free(context->extra);
context->extra = NULL;
}
if (context->rawExif) {
free(context->rawExif);
context->rawExif = NULL;
}
if (context->qtables) {
free(context->qtables);
context->qtables = NULL;
}
jpeg_destroy_compress(&context->cinfo);
/* if (jerr.pub.num_warnings) return BROKEN; */
state->errcode = IMAGING_CODEC_END;
break;
}
/* Return number of bytes in output buffer */
return context->destination.pub.next_output_byte - buf;
}
const char *
ImagingJpegVersion(void) {
static char version[20];
sprintf(version, "%d.%d", JPEG_LIB_VERSION / 10, JPEG_LIB_VERSION % 10);
return version;
}
#endif
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