exif_writer.h File Reference

#include <vector>
#include "image_metadata.h"

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Functions
std::vector< unsigned char >	helios::detail::buildEXIFAppSegment (const ImageEXIFData &m)
	Build the payload of a JPEG APP1 EXIF segment (excludes the 0xFFE1 marker and 2-byte length, which libjpeg writes).
std::vector< unsigned char >	helios::detail::buildXMPAppSegment (const ImageEXIFData &m)
	Build the payload of a JPEG APP1 XMP segment (excludes the 0xFFE1 marker and 2-byte length).

Detailed Description

Hand-rolled EXIF (TIFF/APP1) and XMP (APP1) segment builders for JPEG embedding.

Copyright (C) 2016-2026 Brian Bailey

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

Definition in file exif_writer.h.

Function Documentation

buildEXIFAppSegment()

std::vector< unsigned char > helios::detail::buildEXIFAppSegment

(

const ImageEXIFData &

m

)

Build the payload of a JPEG APP1 EXIF segment (excludes the 0xFFE1 marker and 2-byte length, which libjpeg writes).

The returned buffer begins with the EXIF identifier "Exif\0\0" followed by a little-endian TIFF header, IFD0, ExifSubIFD, and (when m.gps_valid) GPS IFD. Tags whose corresponding fields in m are unset are omitted.

Parameters

[in]

m

Populated metadata struct.

Returns

Byte payload suitable for jpeg_write_marker(&cinfo, JPEG_APP0+1, data, size). Throws via helios_runtime_error if the resulting payload would exceed the JPEG APP1 size limit (65533).

Definition at line 534 of file exif_writer.cpp.

buildXMPAppSegment()

std::vector< unsigned char > helios::detail::buildXMPAppSegment

(

const ImageEXIFData &

m

)

Build the payload of a JPEG APP1 XMP segment (excludes the 0xFFE1 marker and 2-byte length).

The returned buffer begins with the XMP namespace identifier "http://ns.adobe.com/xap/1.0/\0" followed by an RDF/XML packet declaring tiff: and Pix4D Camera: namespaces with Yaw / Pitch / Roll values from m.

Parameters

[in]

m

Populated metadata struct (must have xmp_valid==true to produce a non-empty payload).

Returns

Byte payload suitable for jpeg_write_marker(&cinfo, JPEG_APP0+1, data, size). Throws via helios_runtime_error if the payload exceeds the JPEG APP1 size limit (65533).

Definition at line 639 of file exif_writer.cpp.