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Do cleanup of PNG loading code, in preparation of adding full support…
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… (Issue #90)
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@michaelrsweet
michaelrsweet committed Feb 10, 2025
1 parent 4f1b373 commit 1e5cc6f
Showing 1 changed file with 80 additions and 34 deletions.
114 changes: 80 additions & 34 deletions pdfio-content.c
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Original file line number Diff line number Diff line change
Expand Up @@ -29,12 +29,44 @@
#define _PDFIO_PNG_CHUNK_gAMA 0x67414d41 // Gamma correction
#define _PDFIO_PNG_CHUNK_tRNS 0x74524e53 // Transparency information

#define _PDFIO_PNG_COMPRESSION_FLATE 0 // Flate compression

#define _PDFIO_PNG_FILTER_ADAPTIVE 0 // Adaptive filtering

#define _PDFIO_PNG_INTERLACE_NONE 0 // No interlacing
#define _PDFIO_PNG_INTERLACE_ADAM 1 // "Adam7" interlacing

#define _PDFIO_PNG_TYPE_GRAY 0 // Grayscale
#define _PDFIO_PNG_TYPE_RGB 2 // RGB
#define _PDFIO_PNG_TYPE_INDEXED 3 // Indexed
#define _PDFIO_PNG_TYPE_GRAYA 4 // Grayscale + alpha
#define _PDFIO_PNG_TYPE_RGBA 6 // RGB + alpha


//
// Local types...
//

typedef pdfio_obj_t *(*_pdfio_image_func_t)(pdfio_dict_t *dict, int fd);


//
// Local functions...
//

static pdfio_obj_t *copy_jpeg(pdfio_dict_t *dict, int fd);
static pdfio_obj_t *copy_png(pdfio_dict_t *dict, int fd);
static bool create_cp1252(pdfio_file_t *pdf);
static pdfio_obj_t *create_image(pdfio_file_t *pdf, pdfio_dict_t *dict, const unsigned char *data, size_t width, size_t height, size_t num_colors, bool alpha);
static void ttf_error_cb(pdfio_file_t *pdf, const char *message);
static unsigned update_png_crc(unsigned crc, const unsigned char *buffer, size_t length);
static bool write_string(pdfio_stream_t *st, bool unicode, const char *s, bool *newline);


//
// Local globals...
//

static int _pdfio_cp1252[] = // CP1252-specific character mapping
{
0x20AC,
Expand Down Expand Up @@ -71,31 +103,6 @@ static int _pdfio_cp1252[] = // CP1252-specific character mapping
0x0178
};


//
// Local types...
//

typedef pdfio_obj_t *(*_pdfio_image_func_t)(pdfio_dict_t *dict, int fd);


//
// Local functions...
//

static pdfio_obj_t *copy_jpeg(pdfio_dict_t *dict, int fd);
static pdfio_obj_t *copy_png(pdfio_dict_t *dict, int fd);
static bool create_cp1252(pdfio_file_t *pdf);
static pdfio_obj_t *create_image(pdfio_file_t *pdf, pdfio_dict_t *dict, const unsigned char *data, size_t width, size_t height, size_t num_colors, bool alpha);
static void ttf_error_cb(pdfio_file_t *pdf, const char *message);
static unsigned update_png_crc(unsigned crc, const unsigned char *buffer, size_t length);
static bool write_string(pdfio_stream_t *st, bool unicode, const char *s, bool *newline);


//
// Local globals...
//

static unsigned png_crc_table[256] = // CRC-32 table for PNG files
{
0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419, 0x706af48f,
Expand Down Expand Up @@ -2472,9 +2479,11 @@ copy_png(pdfio_dict_t *dict, // I - Dictionary
crc, // CRC-32
temp, // Temporary value
width = 0, // Width
height = 0; // Height
height = 0, // Height
num_colors = 0; // Number of colors
unsigned char bit_depth = 0, // Bit depth
color_type = 0; // Color type
color_type = 0, // Color type
interlace = 0; // Interlace type
double gamma = 2.2, // Gamma value
wx = 0.0, wy = 0.0, // White point chromacity
rx = 0.0, ry = 0.0, // Red chromacity
Expand Down Expand Up @@ -2583,18 +2592,55 @@ copy_png(pdfio_dict_t *dict, // I - Dictionary
return (NULL);
}

crc = update_png_crc(crc, buffer, length);
width = (unsigned)((buffer[0] << 24) | (buffer[1] << 16) | (buffer[2] << 8) | buffer[3]);
height = (unsigned)((buffer[4] << 24) | (buffer[5] << 16) | (buffer[6] << 8) | buffer[7]);
bit_depth = buffer[8];
crc = update_png_crc(crc, buffer, length);
width = (unsigned)((buffer[0] << 24) | (buffer[1] << 16) | (buffer[2] << 8) | buffer[3]);
height = (unsigned)((buffer[4] << 24) | (buffer[5] << 16) | (buffer[6] << 8) | buffer[7]);

if (width == 0 || height == 0)
{
_pdfioFileError(dict->pdf, "Unsupported PNG dimensions %ux%u.", (unsigned)width, (unsigned)height);
return (NULL);
}

bit_depth = buffer[8];
color_type = buffer[9];

if (width == 0 || height == 0 || (bit_depth != 1 && bit_depth != 2 && bit_depth != 4 && bit_depth != 8 && bit_depth != 16) || (color_type != _PDFIO_PNG_TYPE_GRAY && color_type != _PDFIO_PNG_TYPE_RGB && color_type != _PDFIO_PNG_TYPE_INDEXED) || buffer[10] || buffer[11] || buffer[12])
if (color_type != _PDFIO_PNG_TYPE_GRAY && color_type != _PDFIO_PNG_TYPE_RGB && color_type != _PDFIO_PNG_TYPE_INDEXED)
{
_pdfioFileError(dict->pdf, "Unsupported PNG color type %u.", color_type);
return (NULL);
}

if ((color_type == _PDFIO_PNG_TYPE_GRAY && bit_depth != 1 && bit_depth != 2 && bit_depth != 4 && bit_depth != 8 && bit_depth != 16) ||
(color_type == _PDFIO_PNG_TYPE_RGB && bit_depth != 8 && bit_depth != 16) ||
(color_type == _PDFIO_PNG_TYPE_INDEXED && bit_depth != 1 && bit_depth != 2 && bit_depth != 4 && bit_depth != 8))
{
_pdfioFileError(dict->pdf, "Unsupported PNG image.");
_pdfioFileError(dict->pdf, "Unsupported PNG bit depth %u for color type %u.", bit_depth, color_type);
return (NULL);
}

if (buffer[10] != _PDFIO_PNG_COMPRESSION_FLATE)
{
_pdfioFileError(dict->pdf, "Unsupported PNG compression %u.", buffer[10]);
return (NULL);
}

if (buffer[11] != _PDFIO_PNG_FILTER_ADAPTIVE)
{
_pdfioFileError(dict->pdf, "Unsupported PNG filtering %u.", buffer[11]);
return (NULL);
}

interlace = buffer[12];

if (interlace != _PDFIO_PNG_INTERLACE_NONE)
{
_pdfioFileError(dict->pdf, "Unsupported PNG interlacing %u.", interlace);
return (NULL);
}

num_colors = (color_type == _PDFIO_PNG_TYPE_RGB || color_type == _PDFIO_PNG_TYPE_RGBA) ? 3 : 1;

pdfioDictSetNumber(dict, "Width", width);
pdfioDictSetNumber(dict, "Height", height);
pdfioDictSetNumber(dict, "BitsPerComponent", bit_depth);
Expand All @@ -2604,7 +2650,7 @@ copy_png(pdfio_dict_t *dict, // I - Dictionary
return (NULL);

pdfioDictSetNumber(decode, "BitsPerComponent", bit_depth);
pdfioDictSetNumber(decode, "Colors", color_type == _PDFIO_PNG_TYPE_RGB ? 3 : 1);
pdfioDictSetNumber(decode, "Colors", num_colors);
pdfioDictSetNumber(decode, "Columns", width);
pdfioDictSetNumber(decode, "Predictor", _PDFIO_PREDICTOR_PNG_AUTO);
pdfioDictSetDict(dict, "DecodeParms", decode);
Expand Down

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