Как преобразовать растровое изображение в PIX в памяти?

Ну, я решил сделать это сам с быстрым грязным портом.
Я просто воспользовался функцией загрузки файла BMP и создал поддельный fread / fseek, так как я очень ленив.
Работает.

Если кому-то это понадобится, я опубликую это ниже.
Удивительно, почему разработчики Leptonica не сделали это для Windows должным образом.

#include <cstring>

#include <leptonica/allheaders.h>
#include "leptonica_hack.h"#include "bmp.h"
int fake_file_tracker = 0;

size_t fake_fread ( void * ptr, size_t size, size_t count, char * buffer, size_t buflen)
{
if (fake_file_tracker >= buflen)
{
return 0;
}

if (fake_file_tracker + size * count > buflen)
{
(void)memcpy(ptr, (void *)(buffer+fake_file_tracker), (size_t)(buflen - fake_file_tracker));
fake_file_tracker = buflen+1;
return (size_t)((buflen - fake_file_tracker) / size);
}

(void)memcpy(ptr, (void *)(buffer+fake_file_tracker), size * count);
fake_file_tracker += size * count;
return count;

}

int fake_fseek ( char * buffer, long int offset, int origin, size_t buflen)
{
if (origin + offset >= buflen)
return 0;

fake_file_tracker = origin + offset;
return 0;
}/*!
*  pixReadStreamBmp()
*
*      Input:  stream opened for read
*      Return: pix, or null on error
*
*  Notes:
*      (1) Here are references on the bmp file format:
*          http://en.wikipedia.org/wiki/BMP_file_format
*          http://www.fortunecity.com/skyscraper/windows/364/bmpffrmt.html
*/
PIX *
pixReadBmpFromBuffer(char  *fp, size_t buflen)
{
fake_file_tracker = 0;
l_uint16   sval;
l_uint32   ival;
l_int16    bfType, bfSize, bfFill1, bfReserved1, bfReserved2;
l_int16    offset, bfFill2, biPlanes, depth, d;
l_int32    biSize, width, height, xres, yres, compression, ignore;
l_int32    imagebytes, biClrUsed, biClrImportant;
l_uint8   *colormapBuf = NULL;
l_int32    colormapEntries;
l_int32    fileBpl, extrabytes, readerror;
l_int32    pixWpl, pixBpl;
l_int32    i, j, k;
l_uint8    pel[4];
l_uint8   *data;
l_uint32  *line, *pword;
PIX        *pix, *pixt;
PIXCMAP   *cmap;

PROCNAME("pixReadBmpFromBuffer");

if (!fp)
return (PIX *)ERROR_PTR("fp not defined", procName, NULL);

/* Read bitmap file header */
ignore = fake_fread((char *)&sval, 1, 2, fp, buflen);
bfType = convertOnBigEnd16(sval);
if (bfType != BMP_ID)
return (PIX *)ERROR_PTR("not bmf format", procName, NULL);

ignore = fake_fread((char *)&sval, 1, 2, fp, buflen);
bfSize = convertOnBigEnd16(sval);
ignore = fake_fread((char *)&sval, 1, 2, fp, buflen);
bfFill1 = convertOnBigEnd16(sval);
ignore = fake_fread((char *)&sval, 1, 2, fp, buflen);
bfReserved1 = convertOnBigEnd16(sval);
ignore = fake_fread((char *)&sval, 1, 2, fp, buflen);
bfReserved2 = convertOnBigEnd16(sval);
ignore = fake_fread((char *)&sval, 1, 2, fp, buflen);
offset = convertOnBigEnd16(sval);
ignore = fake_fread((char *)&sval, 1, 2, fp, buflen);
bfFill2 = convertOnBigEnd16(sval);

/* Read bitmap info header */
ignore = fake_fread((char *)&ival, 1, 4, fp, buflen);
biSize = convertOnBigEnd32(ival);
ignore = fake_fread((char *)&ival, 1, 4, fp, buflen);
width = convertOnBigEnd32(ival);
ignore = fake_fread((char *)&ival, 1, 4, fp, buflen);
height = convertOnBigEnd32(ival);
ignore = fake_fread((char *)&sval, 1, 2, fp, buflen);
biPlanes = convertOnBigEnd16(sval);
ignore = fake_fread((char *)&sval, 1, 2, fp, buflen);
depth = convertOnBigEnd16(sval);
ignore = fake_fread((char *)&ival, 1, 4, fp, buflen);
compression = convertOnBigEnd32(ival);
ignore = fake_fread((char *)&ival, 1, 4, fp, buflen);
imagebytes = convertOnBigEnd32(ival);
ignore = fake_fread((char *)&ival, 1, 4, fp, buflen);
xres = convertOnBigEnd32(ival);
ignore = fake_fread((char *)&ival, 1, 4, fp, buflen);
yres = convertOnBigEnd32(ival);
ignore = fake_fread((char *)&ival, 1, 4, fp, buflen);
biClrUsed = convertOnBigEnd32(ival);
ignore = fake_fread((char *)&ival, 1, 4, fp, buflen);
biClrImportant = convertOnBigEnd32(ival);

if (compression != 0)
return (PIX *)ERROR_PTR("cannot read compressed BMP files",
procName,NULL);

/* A little sanity checking.  It would be nice to check
* if the number of bytes in the file equals the offset to
* the data plus the imagedata, but this won't work when
* reading from memory, because fmemopen() doesn't implement
* ftell().  So we can't do that check.  The imagebytes for
* uncompressed images is either 0 or the size of the file data.
* (The fact that it can be 0 is perhaps some legacy glitch).  */
if (width < 1)
return (PIX *)ERROR_PTR("width < 1", procName,NULL);
if (height < 1)
return (PIX *)ERROR_PTR("height < 1", procName,NULL);
if (depth < 1 || depth > 32)
return (PIX *)ERROR_PTR("depth not in [1 ... 32]", procName,NULL);
fileBpl = 4 * ((width * depth + 31)/32);
if (imagebytes != 0 && imagebytes != fileBpl * height)
return (PIX *)ERROR_PTR("invalid imagebytes", procName,NULL);
if (offset < BMP_FHBYTES + BMP_IHBYTES)
return (PIX *)ERROR_PTR("invalid offset: too small", procName,NULL);
if (offset > BMP_FHBYTES + BMP_IHBYTES + 4 * 256)
return (PIX *)ERROR_PTR("invalid offset: too large", procName,NULL);

/* Handle the colormap */
colormapEntries = (offset - BMP_FHBYTES - BMP_IHBYTES) / sizeof(RGBA_QUAD);
if (colormapEntries > 0) {
if ((colormapBuf = (l_uint8 *)CALLOC(colormapEntries,
sizeof(RGBA_QUAD))) == NULL)
return (PIX *)ERROR_PTR("colormapBuf alloc fail", procName, NULL );

/* Read colormap */
if (fake_fread(colormapBuf, sizeof(RGBA_QUAD), colormapEntries, fp, buflen)
!= colormapEntries) {
FREE(colormapBuf);
return (PIX *)ERROR_PTR( "colormap read fail", procName, NULL);
}
}

/* Make a 32 bpp pix if depth is 24 bpp */
d = depth;
if (depth == 24)
d = 32;
if ((pix = pixCreate(width, height, d)) == NULL)
return (PIX *)ERROR_PTR( "pix not made", procName, NULL);
pixSetXRes(pix, (l_int32)((l_float32)xres / 39.37 + 0.5));  /* to ppi */
pixSetYRes(pix, (l_int32)((l_float32)yres / 39.37 + 0.5));  /* to ppi */
pixWpl = pixGetWpl(pix);
pixBpl = 4 * pixWpl;

cmap = NULL;
if (colormapEntries > 256)
L_WARNING("more than 256 colormap entries!", procName);
if (colormapEntries > 0) {  /* import the colormap to the pix cmap */
cmap = pixcmapCreate(L_MIN(d, 8));
FREE(cmap->array);  /* remove generated cmap array */
cmap->array  = (void *)colormapBuf;  /* and replace */
cmap->n = L_MIN(colormapEntries, 256);
}
pixSetColormap(pix, cmap);

/* Seek to the start of the bitmap in the file */
fake_fseek(fp, offset, 0, buflen);

if (depth != 24) {  /* typ. 1 or 8 bpp */
data = (l_uint8 *)pixGetData(pix) + pixBpl * (height - 1);
for (i = 0; i < height; i++) {
if (fake_fread(data, 1, fileBpl, fp, buflen) != fileBpl) {
pixDestroy(&pix);
return (PIX *)ERROR_PTR("BMP read fail", procName, NULL);
}
data -= pixBpl;
}
}
else {  /*  24 bpp file; 32 bpp pix
*  Note: for bmp files, pel[0] is blue, pel[1] is green,
*  and pel[2] is red.  This is opposite to the storage
*  in the pix, which puts the red pixel in the 0 byte,
*  the green in the 1 byte and the blue in the 2 byte.
*  Note also that all words are endian flipped after
*  assignment on L_LITTLE_ENDIAN platforms.
*
*  We can then make these assignments for little endians:
*      SET_DATA_BYTE(pword, 1, pel[0]);      blue
*      SET_DATA_BYTE(pword, 2, pel[1]);      green
*      SET_DATA_BYTE(pword, 3, pel[2]);      red
*  This looks like:
*          3  (R)     2  (G)        1  (B)        0
*      |-----------|------------|-----------|-----------|
*  and after byte flipping:
*           3          2  (B)     1  (G)        0  (R)
*      |-----------|------------|-----------|-----------|
*
*  For big endians we set:
*      SET_DATA_BYTE(pword, 2, pel[0]);      blue
*      SET_DATA_BYTE(pword, 1, pel[1]);      green
*      SET_DATA_BYTE(pword, 0, pel[2]);      red
*  This looks like:
*          0  (R)     1  (G)        2  (B)        3
*      |-----------|------------|-----------|-----------|
*  so in both cases we get the correct assignment in the PIX.
*
*  Can we do a platform-independent assignment?
*  Yes, set the bytes without using macros:
*      *((l_uint8 *)pword) = pel[2];           red
*      *((l_uint8 *)pword + 1) = pel[1];       green
*      *((l_uint8 *)pword + 2) = pel[0];       blue
*  For little endians, before flipping, this looks again like:
*          3  (R)     2  (G)        1  (B)        0
*      |-----------|------------|-----------|-----------|
*/
readerror = 0;
extrabytes = fileBpl - 3 * width;
line = pixGetData(pix) + pixWpl * (height - 1);
for (i = 0; i < height; i++) {
for (j = 0; j < width; j++) {
pword = line + j;
if (fake_fread(&pel, 1, 3, fp, buflen) != 3)
readerror = 1;
*((l_uint8 *)pword + COLOR_RED) = pel[2];
*((l_uint8 *)pword + COLOR_GREEN) = pel[1];
*((l_uint8 *)pword + COLOR_BLUE) = pel[0];
}
if (extrabytes) {
for (k = 0; k < extrabytes; k++)
ignore = fake_fread(&pel, 1, 1, fp, buflen);
}
line -= pixWpl;
}
if (readerror) {
pixDestroy(&pix);
return (PIX *)ERROR_PTR("BMP read fail", procName, NULL);
}
}

pixEndianByteSwap(pix);

/* ----------------------------------------------
* The bmp colormap determines the values of black
* and white pixels for binary in the following way:
* if black = 1 (255), white = 0
*      255, 255, 255, 0, 0, 0, 0, 0
* if black = 0, white = 1 (255)
*      0, 0, 0, 0, 255, 255, 255, 0
* We have no need for a 1 bpp pix with a colormap!
* ---------------------------------------------- */
if (depth == 1 && cmap) {
/*        L_INFO("Removing colormap", procName); */
pixt = pixRemoveColormap(pix, REMOVE_CMAP_BASED_ON_SRC);
pixDestroy(&pix);
pix = pixt;  /* rename */
}

return pix;
}