GPS file properties (FMX)

Question

I can find basic properties of a file with System.IOUtils.TFile like size, date etc. But, i can't figure how to get the GPS coordinates from a JPEG (latitude and longitude) in my C++ Builder FMX app for WIN32.

I can do it with a console application based on this GDI+ example from Microsoft. I just can't figure out how to do this up at System.IOUtils.TFile level. I don't want to run a console app to get the GPS data if don't have to.

Latitude and Longitude are embedded in JPEG images in a structure called EXIF data. I do not think System.IOUtils supports that. But, take a look at the ccr-exif library. — Tom Brunberg
TFile provides access to the file's content, and access to basic metadata from the filesystem only. GPS coordinates are not part of the filesystem metadata. You have to actually open the file and parse its content. There are plenty of JPG parsers available for Delphi if you look around. — Remy Lebeau
Possible duplicate of How to read GPS Coordinates from JPG EXIF using CCR.EXIF in Delphi? — Relinkvent
Thanks Relinkvent, I asked regarding Builder, not Delphi. Have no clue about object pascal. — relayman357
@relayman357 Delphi pascal code can be used in C++Builder projects. — Remy Lebeau

Spektre Spektre · Accepted Answer · 2019-03-25T07:57:11

You can open the exif data on your own ... This is my ancient C++/VCL code doing so:

AnsiString exif_datetime(AnsiString file)
    {
    AnsiString t="";
    int hnd,adr,siz;
    BYTE *dat;
    hnd=FileOpen(file,fmOpenRead);
    if (hnd<0) return t;
    siz=FileSeek(hnd,0,2);
        FileSeek(hnd,0,0);
    dat=new BYTE[siz];
    if (dat==NULL) { FileClose(hnd); return t; }
    siz=FileRead(hnd,dat,siz);
    FileClose(hnd);

    for (adr=0;adr<siz-4;adr++)
        {
        if (dat[adr+0]=='E')
        if (dat[adr+1]=='x')
        if (dat[adr+2]=='i')
        if (dat[adr+3]=='f')
        if (dat[adr+4]== 0 )    // Exif header found
            {
            for (;adr<siz-18;adr++)
                {
                int e=1;
                char a; // "2008:07:17 19:19:10"
                a=dat[adr+ 0]; if ((a<'0')||(a>'9')) e=0;
                a=dat[adr+ 1]; if ((a<'0')||(a>'9')) e=0;
                a=dat[adr+ 2]; if ((a<'0')||(a>'9')) e=0;
                a=dat[adr+ 3]; if ((a<'0')||(a>'9')) e=0;
                a=dat[adr+ 4]; if (a!=':') e=0;
                a=dat[adr+ 5]; if ((a<'0')||(a>'9')) e=0;
                a=dat[adr+ 6]; if ((a<'0')||(a>'9')) e=0;
                a=dat[adr+ 7]; if (a!=':') e=0;
                a=dat[adr+ 8]; if ((a<'0')||(a>'9')) e=0;
                a=dat[adr+ 9]; if ((a<'0')||(a>'9')) e=0;
                a=dat[adr+10]; if (a!=' ') e=0;
                a=dat[adr+11]; if ((a<'0')||(a>'9')) e=0;
                a=dat[adr+12]; if ((a<'0')||(a>'9')) e=0;
                a=dat[adr+13]; if (a!=':') e=0;
                a=dat[adr+14]; if ((a<'0')||(a>'9')) e=0;
                a=dat[adr+15]; if ((a<'0')||(a>'9')) e=0;
                a=dat[adr+16]; if (a!=':') e=0;
                a=dat[adr+17]; if ((a<'0')||(a>'9')) e=0;
                a=dat[adr+18]; if ((a<'0')||(a>'9')) e=0;
                if (e)
                    {
                    for (e=0;e<19;e++) t+=char(dat[adr+e]);
                    break;
                    }
                }
            break;
            }
        }

    delete[] dat;
    return t;
    }

It opens and loads JPG into memory, scan for EXIF structure and if found return date time from it ...

So just extract info you want instead ofthe datetime ... on how to do it see:

Exif standard version 2.31

Its the first file format specs I found (from wiki).

In case you got big images the EXIF in JPG is usually placed at the start of file so you do not need to load the whole image to memory just few first (K)Bytes ...

GPS file properties (FMX)

1 Answers