/* file-png.c

 *

 * Routines for PNG (Portable Network Graphics) image file dissection

 *

 * Copyright 2006 Ronnie Sahlberg

 *

 * Wireshark - Network traffic analyzer

 * By Gerald Combs <gerald@wireshark.org>

 * Copyright 1998 Gerald Combs

 *

 * SPDX-License-Identifier: GPL-2.0-or-later

 */

/* See http://www.w3.org/TR/PNG for specification

 */

#include "config.h"

#include <epan/packet.h>

#include <epan/expert.h>

#include <epan/tfs.h>

#include <wsutil/array.h>

#define MAKE_TYPE_VAL(a, b, c, d)   ((a)<<24 | (b)<<16 | (c)<<8 | (d))

#define CHUNK_TYPE_IHDR   MAKE_TYPE_VAL('I', 'H', 'D', 'R')

#define CHUNK_TYPE_bKGD   MAKE_TYPE_VAL('b', 'K', 'G', 'D')

#define CHUNK_TYPE_gAMA   MAKE_TYPE_VAL('g', 'A', 'M', 'A')

#define CHUNK_TYPE_iCCP   MAKE_TYPE_VAL('i', 'C', 'C', 'P')

#define CHUNK_TYPE_cHRM   MAKE_TYPE_VAL('c', 'H', 'R', 'M')

#define CHUNK_TYPE_pHYs   MAKE_TYPE_VAL('p', 'H', 'Y', 's')

#define CHUNK_TYPE_iTXt   MAKE_TYPE_VAL('i', 'T', 'X', 't')

#define CHUNK_TYPE_tEXt   MAKE_TYPE_VAL('t', 'E', 'X', 't')

#define CHUNK_TYPE_sBIT   MAKE_TYPE_VAL('s', 'B', 'I', 'T')

#define CHUNK_TYPE_sRGB   MAKE_TYPE_VAL('s', 'R', 'G', 'B')

#define CHUNK_TYPE_tIME   MAKE_TYPE_VAL('t', 'I', 'M', 'E')

#define CHUNK_TYPE_IDAT   MAKE_TYPE_VAL('I', 'D', 'A', 'T')

#define CHUNK_TYPE_IEND   MAKE_TYPE_VAL('I', 'E', 'N', 'D')

#define CHUNK_TYPE_tRNS   MAKE_TYPE_VAL('t', 'R', 'N', 'S')

#define CHUNK_TYPE_PLTE   MAKE_TYPE_VAL('P', 'L', 'T', 'E')

static const value_string chunk_types[] = {

    { CHUNK_TYPE_IHDR, "Image Header" },

    { CHUNK_TYPE_bKGD, "Background colour" },

    { CHUNK_TYPE_gAMA, "Image gamma" },

    { CHUNK_TYPE_iCCP, "Embedded ICC profile" },

    { CHUNK_TYPE_cHRM, "Primary chromaticities and white point" },

    { CHUNK_TYPE_pHYs, "Physical pixel dimensions" },

    { CHUNK_TYPE_iTXt, "International textual data" },

    { CHUNK_TYPE_tEXt, "Textual data" },

    { CHUNK_TYPE_sBIT, "Significant bits" },

    { CHUNK_TYPE_sRGB, "Standard RGB colour space" },

    { CHUNK_TYPE_tIME, "Image last-modification time" },

    { CHUNK_TYPE_IDAT, "Image data chunk" },

    { CHUNK_TYPE_IEND, "Image Trailer" },

    { CHUNK_TYPE_tRNS, "Transparency" },

    { CHUNK_TYPE_PLTE, "Palette" },

    { 0, NULL }

};

void proto_register_png(void);

void proto_reg_handoff_png(void);

static const true_false_string png_chunk_anc = {

    "This is an ANCILLARY chunk",

    "This is a CRITICAL chunk"

};

static const true_false_string png_chunk_priv = {

    "This is a PRIVATE chunk",

    "This is a PUBLIC chunk"

};

static const true_false_string png_chunk_stc = {

    "This chunk is SAFE TO COPY",

    "This chunk is NOT safe to copy"

};

static const value_string colour_type_vals[] = {

    { 0,    "Greyscale"},

    { 2,    "Truecolour"},

    { 3,    "Indexed-colour"},

    { 4,    "Greyscale with alpha"},

    { 6,    "Truecolour with alpha"},

    { 0, NULL }

};

static const value_string compression_method_vals[] = {

    { 0,    "Deflate"},

    { 0, NULL }

};

static const value_string filter_method_vals[] = {

    { 0,    "Adaptive"},

    { 0, NULL }

};

static const value_string interlace_method_vals[] = {

    { 0,    "No interlace"},

    { 1,    "Adam7"},

    { 0, NULL }

};

static const value_string srgb_intent_vals[] = {

    { 0, "Perceptual" },

    { 1, "Relative colorimetric" },

    { 2, "Saturation" },

    { 3, "Absolute colorimetric" },

    { 0, NULL }

};

static const value_string phys_unit_vals[] = {

    { 0,    "Unit is unknown"},

    { 1,    "Unit is METRE"},

    { 0, NULL }

};

static int proto_png;

static int hf_png_bkgd_blue;

static int hf_png_bkgd_green;

static int hf_png_bkgd_greyscale;

static int hf_png_bkgd_palette_index;

static int hf_png_bkgd_red;

static int hf_png_chrm_blue_x;

static int hf_png_chrm_blue_y;

static int hf_png_chrm_green_x;

static int hf_png_chrm_green_y;

static int hf_png_chrm_red_x;

static int hf_png_chrm_red_y;

static int hf_png_chrm_white_x;

static int hf_png_chrm_white_y;

static int hf_png_chunk_crc;

static int hf_png_chunk_data;

static int hf_png_chunk_flag_anc;

static int hf_png_chunk_flag_priv;

static int hf_png_chunk_flag_stc;

static int hf_png_chunk_len;

static int hf_png_chunk_type_str;

static int hf_png_gama_gamma;

static int hf_png_ihdr_bitdepth;

static int hf_png_ihdr_colour_type;

static int hf_png_ihdr_compression_method;

static int hf_png_ihdr_filter_method;

static int hf_png_ihdr_height;

static int hf_png_ihdr_interlace_method;

static int hf_png_ihdr_width;

static int hf_png_phys_horiz;

static int hf_png_phys_unit;

static int hf_png_phys_vert;

static int hf_png_signature;

static int hf_png_srgb_intent;

static int hf_png_text_keyword;

static int hf_png_text_string;

static int hf_png_time_day;

static int hf_png_time_hour;

static int hf_png_time_minute;

static int hf_png_time_month;

static int hf_png_time_second;

static int hf_png_time_year;

static int ett_png;

static int ett_png_chunk;

static expert_field ei_png_chunk_too_large;

static dissector_handle_t png_handle;

static void

dissect_png_ihdr(tvbuff_t *tvb, packet_info *pinfo _U_, proto_tree *tree)

{

    proto_tree_add_item(tree, hf_png_ihdr_width, tvb, 0, 4, ENC_BIG_ENDIAN);

    proto_tree_add_item(tree, hf_png_ihdr_height, tvb, 4, 4, ENC_BIG_ENDIAN);

    proto_tree_add_item(tree, hf_png_ihdr_bitdepth, tvb, 8, 1, ENC_BIG_ENDIAN);

    proto_tree_add_item(tree, hf_png_ihdr_colour_type, tvb, 9, 1, ENC_BIG_ENDIAN);

    proto_tree_add_item(tree, hf_png_ihdr_compression_method, tvb, 10, 1, ENC_BIG_ENDIAN);

    proto_tree_add_item(tree, hf_png_ihdr_filter_method, tvb, 11, 1, ENC_BIG_ENDIAN);

    proto_tree_add_item(tree, hf_png_ihdr_interlace_method, tvb, 12, 1, ENC_BIG_ENDIAN);

}

static void

dissect_png_srgb(tvbuff_t *tvb, packet_info *pinfo _U_, proto_tree *tree)

{

    proto_tree_add_item(tree, hf_png_srgb_intent,

            tvb, 0, 1, ENC_BIG_ENDIAN);

}

static void

dissect_png_text(tvbuff_t *tvb, packet_info *pinfo _U_, proto_tree *tree)

{

    int offset=0, nul_offset;

    nul_offset = tvb_find_uint8(tvb, offset, tvb_captured_length_remaining(tvb, offset), 0);

    /* nul_offset == 0 means empty keyword, this is not allowed by the png standard */

    if (nul_offset<=0) {

        /* XXX exception */

        return;

    }

    proto_tree_add_item(tree, hf_png_text_keyword, tvb, offset, nul_offset, ENC_ISO_8859_1);

    offset = nul_offset+1; /* length of the key word + 0 character */

    proto_tree_add_item(tree, hf_png_text_string, tvb, offset, tvb_captured_length_remaining(tvb, offset), ENC_ISO_8859_1);

}

static void

dissect_png_time(tvbuff_t *tvb, packet_info *pinfo _U_, proto_tree *tree)

{

    proto_tree_add_item(tree, hf_png_time_year, tvb, 0, 2, ENC_BIG_ENDIAN);

    proto_tree_add_item(tree, hf_png_time_month, tvb, 2, 1, ENC_BIG_ENDIAN);

    proto_tree_add_item(tree, hf_png_time_day, tvb, 3, 1, ENC_BIG_ENDIAN);

    proto_tree_add_item(tree, hf_png_time_hour, tvb, 4, 1, ENC_BIG_ENDIAN);

    proto_tree_add_item(tree, hf_png_time_minute, tvb, 5, 1, ENC_BIG_ENDIAN);

    proto_tree_add_item(tree, hf_png_time_second, tvb, 6, 1, ENC_BIG_ENDIAN);

}

static void

dissect_png_phys(tvbuff_t *tvb, packet_info *pinfo _U_, proto_tree *tree)

{

    proto_tree_add_item(tree, hf_png_phys_horiz, tvb, 0, 4, ENC_BIG_ENDIAN);

    proto_tree_add_item(tree, hf_png_phys_vert, tvb, 4, 4, ENC_BIG_ENDIAN);

    proto_tree_add_item(tree, hf_png_phys_unit, tvb, 8, 1, ENC_BIG_ENDIAN);

}

static void

dissect_png_bkgd(tvbuff_t *tvb, packet_info *pinfo _U_, proto_tree *tree)

{

    switch(tvb_reported_length(tvb)){

        case 1: /* colour type 3 */

            proto_tree_add_item(tree, hf_png_bkgd_palette_index, tvb, 0, 1, ENC_BIG_ENDIAN);

            break;

        case 2: /* colour type 0, 4 */

            proto_tree_add_item(tree, hf_png_bkgd_greyscale, tvb, 0, 2, ENC_BIG_ENDIAN);

            break;

        case 6: /* colour type 2, 6 */

            proto_tree_add_item(tree, hf_png_bkgd_red, tvb, 0, 2, ENC_BIG_ENDIAN);

            proto_tree_add_item(tree, hf_png_bkgd_green, tvb, 2, 2, ENC_BIG_ENDIAN);

            proto_tree_add_item(tree, hf_png_bkgd_blue, tvb, 4, 2, ENC_BIG_ENDIAN);

            break;

    }

}

static void

dissect_png_chrm(tvbuff_t *tvb, packet_info *pinfo _U_, proto_tree *tree)

{

    float  wx, wy, rx, ry, gx, gy, bx, by;

    int    offset = 0;

    wx = tvb_get_ntohl(tvb, offset) / 100000.0f;

    proto_tree_add_float(tree, hf_png_chrm_white_x,

            tvb, offset, 4, wx);

    offset += 4;

    wy = tvb_get_ntohl(tvb, offset) / 100000.0f;

    proto_tree_add_float(tree, hf_png_chrm_white_y,

            tvb, offset, 4, wy);

    offset += 4;

    rx = tvb_get_ntohl(tvb, offset) / 100000.0f;

    proto_tree_add_float(tree, hf_png_chrm_red_x,

            tvb, offset, 4, rx);

    offset += 4;

    ry = tvb_get_ntohl(tvb, offset) / 100000.0f;

    proto_tree_add_float(tree, hf_png_chrm_red_y,

            tvb, offset, 4, ry);

    offset += 4;

    gx = tvb_get_ntohl(tvb, offset) / 100000.0f;

    proto_tree_add_float(tree, hf_png_chrm_green_x,

            tvb, offset, 4, gx);

    offset += 4;

    gy = tvb_get_ntohl(tvb, offset) / 100000.0f;

    proto_tree_add_float(tree, hf_png_chrm_green_y,

            tvb, offset, 4, gy);

    offset += 4;

    bx = tvb_get_ntohl(tvb, offset) / 100000.0f;

    proto_tree_add_float(tree, hf_png_chrm_blue_x,

            tvb, offset, 4, bx);

    offset += 4;

    by = tvb_get_ntohl(tvb, offset) / 100000.0f;

    proto_tree_add_float(tree, hf_png_chrm_blue_y,

            tvb, offset, 4, by);

}

static void

dissect_png_gama(tvbuff_t *tvb, packet_info *pinfo _U_, proto_tree *tree)

{

    float  gamma;

    gamma = tvb_get_ntohl(tvb, 0) / 100000.0f;

    proto_tree_add_float(tree, hf_png_gama_gamma,

            tvb, 0, 4, gamma);

}

static int

dissect_png(tvbuff_t *tvb, packet_info *pinfo, proto_tree *parent_tree, void *data _U_)

{

    proto_tree *tree;

    proto_item *ti;

    int         offset=0;

    /* http://libpng.org/pub/png/spec/1.2/PNG-Structure.html#PNG-file-signature */

    static const uint8_t magic[8] = { 137, 80, 78, 71, 13, 10, 26, 10 };

    if (tvb_captured_length(tvb) < 20)

        return 0;

    if (tvb_memeql(tvb, 0, magic, sizeof(magic)) != 0)

        return 0;

    col_append_str(pinfo->cinfo, COL_INFO, " (PNG)");

    ti=proto_tree_add_item(parent_tree, proto_png, tvb, offset, -1, ENC_NA);

    tree=proto_item_add_subtree(ti, ett_png);

    proto_tree_add_item(tree, hf_png_signature, tvb, offset, 8, ENC_NA);

    offset+=8;

    while(tvb_reported_length_remaining(tvb, offset) > 0){

        uint32_t    len_field;

        proto_item *len_it;

        proto_tree *chunk_tree;

        uint32_t    type;

        uint8_t    *type_str;

        tvbuff_t   *chunk_tvb;

        len_field = tvb_get_ntohl(tvb, offset);

        type = tvb_get_ntohl(tvb, offset+4);

        type_str = tvb_get_string_enc(pinfo->pool,

                tvb, offset+4, 4, ENC_ASCII|ENC_NA);

        /* 4 byte len field, 4 byte chunk type, 4 byte CRC */

        chunk_tree = proto_tree_add_subtree_format(tree, tvb, offset, 4+4+len_field+4, ett_png_chunk, NULL,

                "%s (%s)", val_to_str_const(type, chunk_types, "unknown"), type_str);

        len_it = proto_tree_add_item(chunk_tree, hf_png_chunk_len,

                tvb, offset, 4, ENC_BIG_ENDIAN);

        offset+=4;

        if (len_field > INT_MAX) {

            expert_add_info(pinfo, len_it, &ei_png_chunk_too_large);

            return offset;

        }

        proto_tree_add_item(chunk_tree, hf_png_chunk_type_str,

                tvb, offset, 4, ENC_ASCII);

        proto_tree_add_item(chunk_tree, hf_png_chunk_flag_anc, tvb, offset, 4, ENC_BIG_ENDIAN);

        proto_tree_add_item(chunk_tree, hf_png_chunk_flag_priv, tvb, offset, 4, ENC_BIG_ENDIAN);

        proto_tree_add_item(chunk_tree, hf_png_chunk_flag_stc, tvb, offset, 4, ENC_BIG_ENDIAN);

        offset+=4;

        chunk_tvb=tvb_new_subset_length(tvb, offset, len_field);

        switch (type) {

            case CHUNK_TYPE_IHDR:

                dissect_png_ihdr(chunk_tvb, pinfo, chunk_tree);

                break;

            case CHUNK_TYPE_bKGD:

                dissect_png_bkgd(chunk_tvb, pinfo, chunk_tree);

                break;

            case CHUNK_TYPE_cHRM:

                dissect_png_chrm(chunk_tvb, pinfo, chunk_tree);

                break;

            case CHUNK_TYPE_gAMA:

                dissect_png_gama(chunk_tvb, pinfo, chunk_tree);

                break;

            case CHUNK_TYPE_pHYs:

                dissect_png_phys(chunk_tvb, pinfo, chunk_tree);

                break;

            case CHUNK_TYPE_sRGB:

                dissect_png_srgb(chunk_tvb, pinfo, chunk_tree);

                break;

            case CHUNK_TYPE_tEXt:

                dissect_png_text(chunk_tvb, pinfo, chunk_tree);

                break;

            case CHUNK_TYPE_tIME:

                dissect_png_time(chunk_tvb, pinfo, chunk_tree);

                break;

            default:

                if (len_field>0) {

                    proto_tree_add_item(chunk_tree, hf_png_chunk_data,

                            tvb, offset, len_field, ENC_NA);

                }

                break;

        }

        offset += len_field;

        proto_tree_add_item(chunk_tree, hf_png_chunk_crc, tvb, offset, 4, ENC_BIG_ENDIAN);

        offset+=4;

    }

    return offset;

}

void

proto_register_png(void)

{

    static hf_register_info hf[] = {

        { &hf_png_signature,

            { "PNG Signature", "png.signature",

              FT_BYTES, BASE_NONE, NULL, 0,

              NULL, HFILL }

        },

        { &hf_png_chunk_data,

            { "Data", "png.chunk.data",

              FT_NONE, BASE_NONE, NULL, 0,

              NULL, HFILL }

        },

        { &hf_png_chunk_type_str,

            { "Type", "png.chunk.type",

              FT_STRING, BASE_NONE, NULL, 0,

              NULL, HFILL }

        },

        { &hf_png_chunk_len,

            { "Len", "png.chunk.len",

              FT_UINT32, BASE_DEC, NULL, 0,

              NULL, HFILL }

        },

        { &hf_png_chunk_crc,

            { "CRC", "png.chunk.crc",

              FT_UINT32, BASE_HEX, NULL, 0,

              NULL, HFILL }

        },

        { &hf_png_chunk_flag_anc,

            { "Ancillary", "png.chunk.flag.ancillary",

              FT_BOOLEAN, 32, TFS(&png_chunk_anc), 0x20000000,

              NULL, HFILL }

        },

        { &hf_png_chunk_flag_priv,

            { "Private", "png.chunk.flag.private",

              FT_BOOLEAN, 32, TFS(&png_chunk_priv), 0x00200000,

              NULL, HFILL }

        },

        { &hf_png_chunk_flag_stc,

            { "Safe To Copy", "png.chunk.flag.stc",

              FT_BOOLEAN, 32, TFS(&png_chunk_stc), 0x00000020,

              NULL, HFILL }

        },

        { &hf_png_ihdr_width,

            { "Width", "png.ihdr.width",

              FT_UINT32, BASE_DEC, NULL, 0,

              NULL, HFILL }

        },

        { &hf_png_ihdr_height,

            { "Height", "png.ihdr.height",

              FT_UINT32, BASE_DEC, NULL, 0,

              NULL, HFILL }

        },

        { &hf_png_ihdr_bitdepth,

            { "Bit Depth", "png.ihdr.bitdepth",

              FT_UINT8, BASE_DEC, NULL, 0,

              NULL, HFILL }

        },

        { &hf_png_ihdr_colour_type,

            { "Colour Type", "png.ihdr.colour_type",

              FT_UINT8, BASE_DEC, VALS(colour_type_vals), 0,

              NULL, HFILL }

        },

        { &hf_png_ihdr_compression_method,

            { "Compression Method", "png.ihdr.compression_method",

              FT_UINT8, BASE_DEC, VALS(compression_method_vals), 0,

              NULL, HFILL }

        },

        { &hf_png_ihdr_filter_method,

            { "Filter Method", "png.ihdr.filter_method",

              FT_UINT8, BASE_DEC, VALS(filter_method_vals), 0,

              NULL, HFILL }

        },

        { &hf_png_ihdr_interlace_method,

            { "Interlace Method", "png.ihdr.interlace_method",

              FT_UINT8, BASE_DEC, VALS(interlace_method_vals), 0,

              NULL, HFILL }

        },

        { &hf_png_srgb_intent,

            { "Intent", "png.srgb.intent",

              FT_UINT8, BASE_DEC, VALS(srgb_intent_vals), 0,

              NULL, HFILL }

        },

        { &hf_png_text_keyword,

            { "Keyword", "png.text.keyword",

              FT_STRING, BASE_NONE, NULL, 0,

              NULL, HFILL }

        },

        { &hf_png_text_string,

            { "String", "png.text.string",

              FT_STRING, BASE_NONE, NULL, 0,

              NULL, HFILL }

        },

        { &hf_png_time_year,

            { "Year", "png.time.year",

              FT_UINT16, BASE_DEC, NULL, 0,

              NULL, HFILL }

        },

        { &hf_png_time_month,

            { "Month", "png.time.month",

              FT_UINT8, BASE_DEC, NULL, 0,

              NULL, HFILL }

        },

        { &hf_png_time_day,

            { "Day", "png.time.day",

              FT_UINT8, BASE_DEC, NULL, 0,

              NULL, HFILL }

        },

        { &hf_png_time_hour,

            { "Hour", "png.time.hour",

              FT_UINT8, BASE_DEC, NULL, 0,

              NULL, HFILL }

        },

        { &hf_png_time_minute,

            { "Minute", "png.time.minute",

              FT_UINT8, BASE_DEC, NULL, 0,

              NULL, HFILL }

        },

        { &hf_png_time_second,

            { "Second", "png.time.second",

              FT_UINT8, BASE_DEC, NULL, 0,

              NULL, HFILL }

        },

        { &hf_png_phys_horiz,

            { "Horizontal pixels per unit", "png.phys.horiz",

              FT_UINT32, BASE_DEC, NULL, 0,

              NULL, HFILL }

        },

        { &hf_png_phys_vert,

            { "Vertical pixels per unit", "png.phys.vert",

              FT_UINT32, BASE_DEC, NULL, 0,

              NULL, HFILL }

        },

        { &hf_png_phys_unit,

            { "Unit", "png.phys.unit",

              FT_UINT8, BASE_DEC, VALS(phys_unit_vals), 0,

              NULL, HFILL }

        },

        { &hf_png_bkgd_palette_index,

            { "Palette Index", "png.bkgd.palette_index",

              FT_UINT8, BASE_DEC, NULL, 0,

              NULL, HFILL }

        },

        { &hf_png_bkgd_greyscale,

            { "Greyscale", "png.bkgd.greyscale",

              FT_UINT16, BASE_HEX, NULL, 0,

              NULL, HFILL }

        },

        { &hf_png_bkgd_red,

            { "Red", "png.bkgd.red",

              FT_UINT16, BASE_HEX, NULL, 0,

              NULL, HFILL }

        },

        { &hf_png_bkgd_green,

            { "Green", "png.bkgd.green",

              FT_UINT16, BASE_HEX, NULL, 0,

              NULL, HFILL }

        },

        { &hf_png_bkgd_blue,

            { "Blue", "png.bkgd.blue",

              FT_UINT16, BASE_HEX, NULL, 0,

              NULL, HFILL }

        },

        { &hf_png_chrm_white_x,

            { "White X", "png.chrm.white.x",

              FT_FLOAT, BASE_NONE, NULL, 0,

              NULL, HFILL }

        },

        { &hf_png_chrm_white_y,

            { "White Y", "png.chrm.white.y",

              FT_FLOAT, BASE_NONE, NULL, 0,

              NULL, HFILL }

        },

        { &hf_png_chrm_red_x,

            { "Red X", "png.chrm.red.x",

              FT_FLOAT, BASE_NONE, NULL, 0,

              NULL, HFILL }

        },

        { &hf_png_chrm_red_y,

            { "Red Y", "png.chrm.red.y",

              FT_FLOAT, BASE_NONE, NULL, 0,

              NULL, HFILL }

        },

        { &hf_png_chrm_green_x,

            { "Green X", "png.chrm.green.x",

              FT_FLOAT, BASE_NONE, NULL, 0,

              NULL, HFILL }

        },

        { &hf_png_chrm_green_y,

            { "Green Y", "png.chrm.green.y",

              FT_FLOAT, BASE_NONE, NULL, 0,

              NULL, HFILL }

        },

        { &hf_png_chrm_blue_x,

            { "Blue X", "png.chrm.blue.x",

              FT_FLOAT, BASE_NONE, NULL, 0,

              NULL, HFILL }

        },

        { &hf_png_chrm_blue_y,

            { "Blue Y", "png.chrm.blue.y",

              FT_FLOAT, BASE_NONE, NULL, 0,

              NULL, HFILL }

        },

        { &hf_png_gama_gamma,

            { "Gamma", "png.gama.gamma",

              FT_FLOAT, BASE_NONE, NULL, 0,

              NULL, HFILL }

        },

    };

    static int *ett[] =

    {

        &ett_png,

        &ett_png_chunk,

    };

    static ei_register_info ei[] = {

        { &ei_png_chunk_too_large,

            { "png.chunk_too_large", PI_PROTOCOL, PI_WARN,

                "chunk size too large, dissection of this chunk is not supported", EXPFILL }}

    };

    expert_module_t *expert_png;

    proto_png = proto_register_protocol("Portable Network Graphics","PNG","png");

    proto_register_field_array(proto_png, hf, array_length(hf));

    proto_register_subtree_array(ett, array_length(ett));

    expert_png = expert_register_protocol(proto_png);

    expert_register_field_array(expert_png, ei, array_length(ei));

    png_handle = register_dissector("png", dissect_png, proto_png);

}

static bool dissect_png_heur(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data)

{

    return dissect_png(tvb, pinfo, tree, data) > 0;

}

void

proto_reg_handoff_png(void)

{

    dissector_add_string("media_type", "image/png", png_handle);

    heur_dissector_add("http", dissect_png_heur, "PNG file in HTTP", "png_http", proto_png, HEURISTIC_ENABLE);

    heur_dissector_add("wtap_file", dissect_png_heur, "PNG file in HTTP", "png_wtap", proto_png, HEURISTIC_ENABLE);

}

/*

 * Editor modelines  -  https://www.wireshark.org/tools/modelines.html

 *

 * Local variables:

 * c-basic-offset: 4

 * tab-width: 8

 * indent-tabs-mode: nil

 * End:

 *

 * vi: set shiftwidth=4 tabstop=8 expandtab:

 * :indentSize=4:tabSize=8:noTabs=true:

 */