From 79c276f94d448f9815714a231509a35ec2fe1702 Mon Sep 17 00:00:00 2001
From: wp_xxyyzz <wp_xxyyzz@8e941d3f-bd1b-0410-a28a-d453659cc2b4>
Date: Sat, 30 Jan 2021 13:02:03 +0000
Subject: [PATCH] fpexif: combine value and unit field of some GPS tags to
 direct Exifdata properties. Issue #38423.

git-svn-id: https://svn.code.sf.net/p/lazarus-ccr/svn@7968 8e941d3f-bd1b-0410-a28a-d453659cc2b4
---
 components/fpexif/fpeexifdata.pas | 56 +++++++++++++++++++++++++++++++
 1 file changed, 56 insertions(+)

diff --git a/components/fpexif/fpeexifdata.pas b/components/fpexif/fpeexifdata.pas
index 0de5e126e..fe9b1a0dc 100644
--- a/components/fpexif/fpeexifdata.pas
+++ b/components/fpexif/fpeexifdata.pas
@@ -59,11 +59,13 @@ type
     function GetImgHeight: Integer;
     function GetImgWidth: Integer;
     function GetOrientation: TExifOrientation;
+    function GetGPSPosition(AKind: Integer): double;
     function GetTagByID(ATagID: TTagID): TTag;
     function GetTagByIndex(AIndex: Integer): TTag;
     function GetTagByName(AFullTagName: String): TTag;
     function GetTagCount: Integer;
     procedure SetExportOptions(const AValue: TExportOptions);
+    procedure SetGPSPosition(AKind: Integer; AValue: Double);
     procedure SetTagByID(ATagID: TTagID; ATag: TTag);
     procedure SetTagByIndex(AIndex: Integer; ATag: TTag);
     procedure SetTagByName(AFullTagName: String; ATag: TTag);
@@ -129,12 +131,16 @@ type
     property TagCount: Integer
       read GetTagCount;
 
+    // Special tags
     property ImgHeight: Integer
       read GetImgHeight;
     property ImgWidth: Integer
       read GetImgWidth;
     property ImgOrientation: TExifOrientation
       read GetOrientation;
+    property GPSAltitude: Double index 2 read GetGPSPosition write SetGPSPosition;
+    property GPSLatitude: Double index 1 read GetGPSPosition write SetGPSPosition;
+    property GPSLongitude: Double index 0 read GetGPSPosition write SetGPSPosition;
 
     property OnBeginReading: TExifBeginReadingEvent
       read FOnBeginReading write FOnBeginReading;
@@ -274,6 +280,17 @@ uses
   Math, DateUtils, StrUtils,
   fpeStrConsts, fpeUtils;
 
+const
+  GPSPositionTags: array[0..2] of string = (
+    'GPSLongitude', 'GPSLatitude', 'GPSAltitude'
+  );
+  GPSPositionRefTags: array[0..2] of string = (
+    'GPSLongitudeRef', 'GPSLatitudeRef', 'GPSAltitudeRef'
+  );
+  PosGPSRef: array[0..2] of String = ('E', 'N', '');
+  NegGPSRef: array[0..2] of String = ('W', 'S', '');
+
+
 //==============================================================================
 //                         Tag definitions (TagDef)
 //==============================================================================
@@ -885,6 +902,27 @@ begin
 end;
 
 
+{ Combines the GPS<kind> and GPS<kind>Ref tags for Longitude (AKind = 0),
+  Latitude (AKind = 1), Aligutude (AKind = 2) to a floating point value }
+function TExifdata.GetGPSPosition(AKind: Integer): double;
+var
+  tag: TTag;
+begin
+  Result := NaN;
+
+  tag := TagByName[GPSPositionTags[AKind]];
+  if (tag = nil) then
+    exit;
+  Result := TGPSPositionTag(tag).AsFloat;
+
+  tag := TagByName[GPSPositionRefTags[AKind]];
+  if Assigned(tag) then
+    case AKind of
+      0..1: if (tag.AsString[1] = NegGPSRef[AKind]) then Result := -Result;
+      2   : if (tag.AsInteger = 1) then Result := -Result;
+    end;
+end;
+
 { Finds the tag which defines the sub-IFD to which the specified tag belongs }
 function TExifData.GetParentTag(ATag: TTag): TTag;
 var
@@ -1104,6 +1142,24 @@ begin
   end;
 end;
 
+procedure TExifData.SetGPSPosition(AKind: Integer; AValue: Double);
+var
+  tag: TTag;
+begin
+  tag := TagByName[GPSPositionTags[AKind]];
+  if tag = nil then
+    tag := AddTagByName(GPSPositionTags[AKind]);
+  tag.AsFloat := abs(AValue);
+
+  tag := TagByName[GPSPositionRefTags[AKind]];
+  if tag = nil then
+    tag := AddTagByName(GPSPositionRefTags[AKind]);
+  case AKind of
+    0..1: if AValue >= 0 then tag.AsString := PosGPSRef[AKind] else tag.AsString := NegGPSRef[AKind];
+    2   : if AValue >= 0 then tag.AsInteger := 0 else tag.AsInteger := 1;
+  end;
+end;
+
 procedure TExifData.SetTagByID(ATagID: TTagID; ATag: TTag);
 var
   idx: Integer;