exif read : warnings and errors : Potentially invalid endianess, Illegal IFD size and Undefined index

[Ben29980]

Hello community,
I read that on older php versions exif read function was not working properly on certain images.
I should have been patched with new php versions... But not fully...

On recent DJI images, I have a persistent uncapacity to correctly "read exif data" from image

Image example:

here an example of errors I have:

Please note that with other images, it works like a charm. And not problem for me to extract data.

Here is my code:
`//get the EXIF
$exif = exif_read_data($file, 'IFD0');
echo $exif===false ? "Aucun en-tête de donnés n'a été trouvé.
\n" : "L'image contient des en-têtes
\n";
$exif = exif_read_data($file);

//get the Hemisphere multiplier
$LatM = 1; 
$LongM = 1;
if($exif["GPSLatitudeRef"] == 'S')
{
$LatM = -1;
}
if($exif["GPSLongitudeRef"] == 'W')
{
$LongM = -1;
}

$alt      = explode('/', $exif["GPSAltitude"]);
$altitude = (isset($alt[1])) ? ($alt[0] / $alt[1]) : $alt[0];

//get the GPS data
$gps['LatDegree']=$exif["GPSLatitude"][0];
$gps['LatMinute']=$exif["GPSLatitude"][1];
$gps['LatgSeconds']=$exif["GPSLatitude"][2];
$gps['LongDegree']=$exif["GPSLongitude"][0];
$gps['LongMinute']=$exif["GPSLongitude"][1];
$gps['LongSeconds']=$exif["GPSLongitude"][2];`

[Girgias]

What PHP version are you running? (also this is probably more a php-src issue then a doc issue)

[cmb69]

also this is probably more a php-src issue then a doc issue

Right. Transferring.

[cmb69]

The problem is that this image has a makernote with an uncommon (non-standard?) format which contains the DJI Info Tags. Since there is no special support for reading this, the reading fails early, and that causes quite some information to be missing from the exif_read_data() results.

I have not been able to find some normative information about this format, but the following work-around might be a start:

 ext/exif/exif.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/ext/exif/exif.c b/ext/exif/exif.c
index a6db8745b3..51545f74cc 100644
--- a/ext/exif/exif.c
+++ b/ext/exif/exif.c
@@ -3170,6 +3170,10 @@ static bool exif_process_IFD_in_MAKERNOTE(image_info_type *ImageInfo, char * val
 
 	dir_start = value_ptr + maker_note->offset;
 
+	if (!strcmp(maker_note->make, "DJI") && *dir_start == '[') {
+		return true;
+	}
+
 #ifdef EXIF_DEBUG
 	exif_error_docref(NULL EXIFERR_CC, ImageInfo, E_NOTICE, "Process %s @x%04X + 0x%04X=%d: %s", exif_get_sectionname(section_index), (intptr_t)dir_start-(intptr_t)info->offset_base+maker_note->offset+displacement, value_len, value_len, exif_char_dump(value_ptr, value_len, (intptr_t)dir_start-(intptr_t)info->offset_base+maker_note->offset+displacement));
 #endif

That would yield:

array(70) {
  ["FileName"]=>
  string(10) "gh1760.jpg"
  ["FileDateTime"]=>
  int(1661168285)
  ["FileSize"]=>
  int(9142758)
  ["FileType"]=>
  int(2)
  ["MimeType"]=>
  string(10) "image/jpeg"
  ["SectionsFound"]=>
  string(51) "ANY_TAG, IFD0, THUMBNAIL, EXIF, GPS, INTEROP, WINXP"
  ["COMPUTED"]=>
  array(8) {
    ["html"]=>
    string(26) "width="4056" height="3040""
    ["Height"]=>
    int(3040)
    ["Width"]=>
    int(4056)
    ["IsColor"]=>
    int(1)
    ["ByteOrderMotorola"]=>
    int(0)
    ["ApertureFNumber"]=>
    string(5) "f/2.8"
    ["Thumbnail.FileType"]=>
    int(2)
    ["Thumbnail.MimeType"]=>
    string(10) "image/jpeg"
  }
  ["ImageDescription"]=>
  string(7) "default"
  ["Make"]=>
  string(3) "DJI"
  ["Model"]=>
  string(5) "ZH20T"
  ["Orientation"]=>
  int(1)
  ["XResolution"]=>
  string(4) "72/1"
  ["YResolution"]=>
  string(4) "72/1"
  ["ResolutionUnit"]=>
  int(2)
  ["Software"]=>
  string(11) "04.00.00.10"
  ["DateTime"]=>
  string(19) "2022:08:13 10:18:19"
  ["YCbCrPositioning"]=>
  int(2)
  ["Exif_IFD_Pointer"]=>
  int(260)
  ["GPS_IFD_Pointer"]=>
  int(710)
  ["Comments"]=>
  string(7) "0.9.142"
  ["Keywords"]=>
  string(6) "single"
  ["THUMBNAIL"]=>
  array(6) {
    ["Compression"]=>
    int(7)
    ["XResolution"]=>
    string(4) "72/1"
    ["YResolution"]=>
    string(4) "72/1"
    ["ResolutionUnit"]=>
    int(2)
    ["JPEGInterchangeFormat"]=>
    int(24962)
    ["JPEGInterchangeFormatLength"]=>
    int(11927)
  }
  ["ExposureTime"]=>
  string(5) "1/725"
  ["FNumber"]=>
  string(7) "280/100"
  ["ExposureProgram"]=>
  int(2)
  ["ISOSpeedRatings"]=>
  int(110)
  ["UndefinedTag:0x8830"]=>
  int(2)
  ["ExifVersion"]=>
  string(4) "0230"
  ["DateTimeOriginal"]=>
  string(19) "2022:08:13 10:18:19"
  ["DateTimeDigitized"]=>
  string(19) "2022:08:13 10:18:19"
  ["ComponentsConfiguration"]=>
  string(4) "���"
  ["ShutterSpeedValue"]=>
  string(11) "95018/10000"
  ["ApertureValue"]=>
  string(7) "297/100"
  ["ExposureBiasValue"]=>
  string(4) "0/10"
  ["MaxApertureValue"]=>
  string(7) "297/100"
  ["MeteringMode"]=>
  int(2)
  ["LightSource"]=>
  int(1)
  ["Flash"]=>
  int(0)
  ["FocalLength"]=>
  string(9) "4500/1000"
  ["MakerNote"]=>
  string(13) "[ae_dbg_info:"
  ["FlashPixVersion"]=>
  string(4) "0100"
  ["ColorSpace"]=>
  int(1)
  ["ExifImageWidth"]=>
  int(4056)
  ["ExifImageLength"]=>
  int(3040)
  ["InteroperabilityOffset"]=>
  int(824)
  ["FileSource"]=>
  string(1) "�"
  ["SceneType"]=>
  string(1) "�"
  ["ExposureMode"]=>
  int(0)
  ["WhiteBalance"]=>
  int(0)
  ["DigitalZoomRatio"]=>
  string(7) "100/100"
  ["FocalLengthIn35mmFilm"]=>
  int(24)
  ["SceneCaptureType"]=>
  int(0)
  ["GainControl"]=>
  int(0)
  ["Contrast"]=>
  int(0)
  ["Saturation"]=>
  int(0)
  ["Sharpness"]=>
  int(0)
  ["DeviceSettingDescription"]=>
  string(4) ""
  ["UndefinedTag:0xA431"]=>
  string(14) "1W9DK5T001EV6H"
  ["UndefinedTag:0xA432"]=>
  array(4) {
    [0]=>
    string(9) "4500/1000"
    [1]=>
    string(9) "4500/1000"
    [2]=>
    string(7) "280/100"
    [3]=>
    string(7) "280/100"
  }
  ["GPSVersion"]=>
  string(4) "��"
  ["GPSLatitudeRef"]=>
  string(1) "N"
  ["GPSLatitude"]=>
  array(3) {
    [0]=>
    string(4) "46/1"
    [1]=>
    string(3) "9/1"
    [2]=>
    string(12) "388800/10000"
  }
  ["GPSLongitudeRef"]=>
  string(1) "E"
  ["GPSLongitude"]=>
  array(3) {
    [0]=>
    string(3) "5/1"
    [1]=>
    string(4) "39/1"
    [2]=>
    string(12) "403541/10000"
  }
  ["GPSAltitudeRef"]=>
  string(1) ""
  ["GPSAltitude"]=>
  string(11) "760236/1000"
  ["GPSStatus"]=>
  string(1) "A"
  ["GPSMapDatum"]=>
  string(6) "WGS-84"
  ["InterOperabilityIndex"]=>
  string(3) "R98"
  ["InterOperabilityVersion"]=>
  string(4) "0100"
}

[Ben29980]

What PHP version are you running? (also this is probably more a php-src issue then a doc issue)

My PHP version is 8.1.0.

The problem is that this image has a makernote with an uncommon (non-standard?) format which contains the DJI Info Tags. Since there is no special support for reading this, the reading fails early, and that causes quite some information to be missing from the exif_read_data() results.

I have not been able to find some normative information about this format, but the following work-around might be a start:

 ext/exif/exif.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/ext/exif/exif.c b/ext/exif/exif.c
index a6db8745b3..51545f74cc 100644
--- a/ext/exif/exif.c
+++ b/ext/exif/exif.c
@@ -3170,6 +3170,10 @@ static bool exif_process_IFD_in_MAKERNOTE(image_info_type *ImageInfo, char * val
 
 	dir_start = value_ptr + maker_note->offset;
 
+	if (!strcmp(maker_note->make, "DJI") && *dir_start == '[') {
+		return true;
+	}
+
 #ifdef EXIF_DEBUG
 	exif_error_docref(NULL EXIFERR_CC, ImageInfo, E_NOTICE, "Process %s @x%04X + 0x%04X=%d: %s", exif_get_sectionname(section_index), (intptr_t)dir_start-(intptr_t)info->offset_base+maker_note->offset+displacement, value_len, value_len, exif_char_dump(value_ptr, value_len, (intptr_t)dir_start-(intptr_t)info->offset_base+maker_note->offset+displacement));
 #endif

That would yield:

Thanks @cmb69, do you think that native php exif read function could be updated ?
Or should I use a php exiftools library ?

[cmb69]

Completely failing to parse other EXIF data after parsing the maker note failed, is a bug, and should be fixed (not sure how; patch above is more like a PoC). Being able to parse DJI info tags is more like a feature request, though.

[Ben29980]

Completely failing to parse other EXIF data after parsing the maker note failed, is a bug, and should be fixed (not sure how; patch above is more like a PoC). Being able to parse DJI info tags is more like a feature request, though.

Thanks @cmb69 , should I open a feature request ?

[cmb69]

should I open a feature request ?

Feel free to open a new ticket. However, someone needs to implement that. :)

[akkana]

I'm not sure if I'm in the right issue, but I'm seeing the "Illegal IFD size" warning when I call exif_read_data() on https://shallowsky.com/images/annular-eclipse-2012/img_5405.jpg (among other images). It doesn't fail to parse the rest of the exif, it's just an annoying warning cluttering my server logs. exiftool shows the image's EXIF without any complaints. exiftool also doesn't show anything matching "dji", "maker" or "note". I'm not sure what PHP is complaining about or how to fix it since the warning isn't specific.