Mailing lists / lazarus / 2016-09
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Hi,
I have JPEG image with width=2448 and height=3264.
All programs in Windows show image with respect to his dimensions, so shorter is X and higher is Y.
But when I load this image into TImage control (using Picture property) image is shown rotated by 90 degrees, with width=3264 and height=2448
Original image is on
http://moja.uschovna.zoznam.sk/link/c13c4eb8-c035-4879-879e-de04f8e9c13c
All what is needed for reproducing is put TImage on TForm and load picture ...
Why this happens ?
TIA
-Laco.
LacaK wroteHi, I have JPEG image with width=2448 and height=3264.
No
That is correct. If you look at the exif info, you read:
Filename - 6.jpg
...
ImageWidth - 3264
ImageLength - 2448
...
ExifImageWidth - 3264
ExifImageHeight - 2448
...
Orientation - Right top
What you see is the result of "smart" image viewers, which read the exif info and read that you held the camera sideways and there fore rotate the image.
the image istself is still 3264x2448
Marc
Dňa 23.9.2016 o 14:47 Marc Weustink napísal(a):
How do you read this Exif info ?
When I right click image and look at Details tab I see there only width=2448 and height=3264
But when I use on-line exif viewer (at http://regex.info/exif.cgi) there are swaped results and:
OrientationRotate = 90 CW
So it seems, that you are right ;-)
Next question then is: how can I detect this in Lazarus and do same as "smart viewers" do ?
(in other words: is there and component, which allows me read this EXIF information from JPEG image ?)
Thanks
-Laco.
with a decent viewer ;) (in windows I use irfanview)
When I right click image and look at Details tab I see there only width=2448 and height=3264
I see too
Google ?
Exif + Delphi -> torry.net -> NativeJpg v.1.33 or TExif v.1.3 or TGJPGCommentInfoP v.1.0
(looking for sources supporting D7)
you may try that.
Marc
I have created small Exif reader for my own needs. I have looked also in FCL TFPReaderJpeg (which uses pasjpeg) if there is no support, but I do not see.
If there would be interest for extending functionality of this reader to support reading of Exif information I can prepare patch.
Here is my simple implementation if somebody is interested:
======================================================================== { TJpegExifReader }
TJpegExifReader = class
private
type
TIFDEntry = record
TagNo: Word;
DataType: Word;
Count: DWord;
Value: DWord; // This tag records the offset from the
start of the TIFF header to the position where the value
itself is recorded.
// In cases where the value fits in 4 bytes,
the value itself is recorded. If the value is smaller than 4 bytes, the
value is stored in the 4-byte area starting from the left, i.e., from
the lower end
end;
TExifData = record
Make,
Model,
Software,
DateTime: string;
Orientation: smallint;
XResolution,
YResolution: double;
ResolutionUnit: smallint;
end;
var
FBA: Word;
function Swap(w: Word): Word; overload;
protected
FIFD: array of TIFDEntry;
FExif: TExifData;
public
constructor Create(const FileName: string); overload;
constructor Create(Stream: TFileStream); overload;
function Orientation: smallint;
function XResolution: double;
function YResolution: double;
function ResolutionUnit: string;
function DateTime: TDateTime;
end;{ TJpegExifReader }
function TJpegExifReader.Swap(w: Word): Word;
begin
if FBA = $4D4D then
// Motorola align: first byte in data is highest byte (big endian)
Result := BEtoN(w)
else
// Intel align: first byte in data is lowest byte (little endian)
Result := LEtoN(w);
end;
constructor TJpegExifReader.Create(const FileName: string);
var
Stream: TFileStream;
begin
Stream := TFileStream.Create(FileName, fmOpenRead+fmShareDenyWrite);
try
Create(Stream);
finally
Stream.Free;
end;
end;
constructor TJpegExifReader.Create(Stream: TFileStream);
type
TRATIONAL=record
numerator: dword;
denominator: dword;
end;
var
w, Size: word;
dw: dword;
n,i,c: integer;
S: AnsiString;
R: TRATIONAL;
D: double;
begin
inherited Create;
Stream.Position := 0;
Stream.Read(w,SizeOf(w));
if w NtoLE($D8FF) then Exit; // 0-1: Jpeg SOI (Start of
image: FFD8)
Stream.Read(w, SizeOf(w));
if w NtoLE($E1FF) then Exit; // 2-3: APP1 (Application
marker: FFE1)
Stream.Read(Size, SizeOf(Size)); // 4-5: Size of APP1 data area
(high byte first)
Size := BEtoN(Size);
Dec(Size, 2);
// Exif
Stream.Read(dw, SizeOf(dw));
if dw NtoLE($66697845) then Exit; // 6-9: 'Exif'
Stream.Read(w, SizeOf(w));
if w NtoLE($0000) then Exit; // 10-11: 0000
Dec(Size, 6);
// TIFF header
Stream.Read(FBA, SizeOf(FBA)); // 12-13: byte order
if (FBA$4949) and (FBA$4D4D) then Exit; // 4949=Intel, 4D4D=Motorola
Stream.Read(w, SizeOf(w));
if Swap(w) $002A then Exit; // Tag Mark
Stream.Read(dw, SizeOf(dw)); // Offset to first IFD (usualy 8)
Dec(Size, 8);
// IFD: Image file directory
SetLength(FIFD, 0);
Stream.Read(w, SizeOf(w)); // No of IFD entries
Dec(Size, 2);
n := Swap(w);
SetLength(FIFD, Length(FIFD)+n);
// Read IFD entries
for i:=0 to n-1 do begin
Stream.Read(FIFD[i], SizeOf(TIFDEntry));
Dec(Size, SizeOf(TIFDEntry));
end;
Stream.Read(dw, SizeOf(dw)); // Offset to next IFD (0=last)
// Parse IFD entries
for i:=0 to n-1 do begin
case Swap(FIFD[i].DataType) of
1: w:=1; // unsigned byte
2: w:=1; // ascii string (terminated with 0)
3: w:=2; // unsigned short (2 bytes)
4: w:=4; // unsigned long (4 bytes)
5: w:=8; // unsigned rational (4+4 long)
else w:=1;
end;
c := w * Swap(FIFD[i].Count);
if c > 4 then begin
// Value contains offset from TIFF header to data
Stream.Position := 12 + Swap(FIFD[i].Value);
case Swap(FIFD[i].DataType) of
2: begin
Dec(c);
SetLength(S, c);
Stream.Read(S[1], c);
end;
5: begin
Stream.Read(R, SizeOf(R));
D := R.numerator / R.denominator;
end;
end;
end
else
case Swap(FIFD[i].DataType) of
3: w := Swap(FIFD[i].Value);
end;
case Swap(FIFD[i].TagNo) of
$010F: FExif.Make := S;
$0110: FExif.Model := S;
$0112: FExif.Orientation := w;
$011A: FExif.XResolution := D;
$011B: FExif.YResolution := D;
$0128: FExif.ResolutionUnit := w;
$0131: FExif.Software := S;
$0132: FExif.DateTime := S;
$8769: // offset to Exif SubIFD
end;
end;
end;
function TJpegExifReader.Orientation: smallint;
begin
case FExif.Orientation of
3: Result := 180;
6: Result := 270; // The 0th row is the visual right-hand side of
the image, and the 0th column is the visual top.
else Result := 0;
end;
end;
function TJpegExifReader.XResolution: double;
begin
Result := FExif.XResolution;
end;
function TJpegExifReader.YResolution: double;
begin
Result := FExif.YResolution;
end;
function TJpegExifReader.ResolutionUnit: string;
begin
case FExif.ResolutionUnit of
2: Result := 'in';
3: Result := 'cm';
else Result := '';
end;
end;
function TJpegExifReader.DateTime: TDateTime;
begin
Result := ComposeDateTime(
StrToDate(Copy(FExif.DateTime,1,10), 'yyyy:mm:dd', ':'),
StrToTime(Copy(FExif.DateTime,12,8), ':')
);
end;========================================================================
There is interest :)
Michael.
Hm, looking deeper into TFPCustomImageReader architecture intention of such readers is constitute TFPCustomImage.
Now I am not sure where metadata (Exif) should go ? (As far as TFPCustomImage holds only true image data)
I can extend TFPReaderJpeg, by adding boolean option ("ReadExif") either to constructor or as a standalone property, which will signal to reader if read also this kind of data.
If set to true then in "InternalRead" I can read from supplied stream and store them in record inside TFPReaderJpeg ... so user must ask reader later to obtain exif data
Or do not touch TReaderJpeg and add only new "helper" class which will read from supplied stream exif data (just as in source which I have attached to my prior mail)
What do you prefer ?
-Laco.
I have created small Exif reader for my own needs. I have looked also in FCL…
This is great! Please do, if you have time.
Anyway, thanks for this code.
Thierry
Attached improved code.
(as far as there is a lot of Exif tags, not all are parsed and placed in FExif record, but all are in FIFD array)
-Laco.
-------------- next part --------------
unit JpegExif;
{$IFDEF FPC}
{$mode objfpc}
{$ENDIF}
{$H+}
interface
uses
Classes, SysUtils;
type
{ TJpegExifReader }
TJpegExifReader = class
private
type
TIFDEntry = record
TagNo: Word;
DataType: Word;
Count: DWord;
Value: DWord; // This tag records the offset from the start of the TIFF header to the position where the value itself is recorded.
// In cases where the value fits in 4 bytes, the value itself is recorded. If the value is smaller than 4 bytes, the value is stored in the 4-byte area starting from the left, i.e., from the lower end
end;
TExifData = record
Make,
Model,
Software,
DateTime,
Artist: string;
Orientation: smallint;
XResolution,
YResolution: double;
ResolutionUnit: smallint;
ExposureTime: double;
FNumber: double;
ColorSpace: Word;
ImageUniqueID: string;
end;
var
FBA: Word;
function Swap(w: Word): Word; overload;
function Swap(dw: DWord): DWord; overload;
public
FIFD: array of TIFDEntry;
FExif: TExifData;
public
constructor Create(const FileName: string); overload;
constructor Create(Stream: TFileStream); overload;
function Orientation: smallint;
function XResolution: double;
function YResolution: double;
function ResolutionUnit: string;
function DateTime: TDateTime;
end;
implementation{ TJpegExifReader }
function TJpegExifReader.Swap(w: Word): Word;
begin
if FBA = $4D4D then
// Motorola align: first byte in data is highest byte (big endian)
Result := BEtoN(w)
else
// Intel align: first byte in data is lowest byte (little endian)
Result := LEtoN(w);
end;
function TJpegExifReader.Swap(dw: DWord): DWord;
begin
if FBA = $4D4D then
Result := BEtoN(dw)
else
Result := LEtoN(dw);
end;
constructor TJpegExifReader.Create(const FileName: string);
var
Stream: TFileStream;
begin
Stream := TFileStream.Create(FileName, fmOpenRead+fmShareDenyWrite);
try
Create(Stream);
finally
Stream.Free;
end;
end;
constructor TJpegExifReader.Create(Stream: TFileStream);
type
TRATIONAL=record
numerator: dword;
denominator: dword;
end;
var
b: Byte;
w, Marker, Size: Word;
dw: DWord;
i,c: Integer;
S: AnsiString;
R: TRATIONAL;
D: Double;
function ReadIFD(Offset: DWord): integer;
var i,j: integer;
begin
Stream.Position := 12 + Offset;
Stream.Read(w, SizeOf(w)); // No of IFD entries
Dec(Size, 2);
Result := Swap(w);
j := Length(FIFD);
SetLength(FIFD, j+Result);
// Read IFD entries
for i:=j to j+Result-1 do begin
Stream.Read(FIFD[i], SizeOf(TIFDEntry));
Dec(Size, SizeOf(TIFDEntry));
FIFD[i].TagNo := Swap(FIFD[i].TagNo);
FIFD[i].DataType := Swap(FIFD[i].DataType);
FIFD[i].Count := Swap(FIFD[i].Count);
end;
Stream.Read(dw, SizeOf(dw)); // Offset to next IFD (0=last)
end;
begin
inherited Create;
Stream.Position := 0;
Stream.Read(w,SizeOf(w));
if w NtoLE($D8FF) then Exit; // 0-1: Jpeg SOI (Start of image: FFD8)
Stream.Read(Marker, SizeOf(w)); // 2-3: Application marker
Stream.Read(Size, SizeOf(Size)); // 4-5: Size of APP1 data area (high byte first)
Size := BEtoN(Size);
Dec(Size, 2);
Stream.Read(dw, SizeOf(dw)); // 6-9: 'Exif' of 'JFIF'
Dec(Size, 4);
// APP0 (Application marker: FFE0) and 'JFIF'
if (Marker = NtoLE($E0FF)) and (dw = NtoLE($4649464A)) then
begin
Stream.Read(b, 1); // 10: 0
Stream.Read(w, SizeOf(w)); // 11-12: JFIF version
Stream.Read(b, 1); // 13: Density units (1-in, 2-px)
FExif.ResolutionUnit := b+1;
Stream.Read(w, SizeOf(w)); // 14-15: XDensity
FExif.XResolution := BEtoN(w);
Stream.Read(w, SizeOf(w)); // 16-17: YDensity
FExif.YResolution := BEtoN(w);
end
// APP1 (Application marker: FFE1) and 'Exif'
else if (Marker = NtoLE($E1FF)) and (dw = NtoLE($66697845)) then
begin
Stream.Read(w, SizeOf(w));
if w NtoLE($0000) then Exit; // 10-11: 0000
Dec(Size, 2);
// TIFF header
Stream.Read(FBA, SizeOf(FBA)); // 12-13: byte order
if (FBA$4949) and (FBA$4D4D) then Exit; // 4949=Intel, 4D4D=Motorola
Stream.Read(w, SizeOf(w));
if Swap(w) $002A then Exit; // Tag Mark
Stream.Read(dw, SizeOf(dw)); // Offset to first IFD (usualy 8)
Dec(Size, 8);
// IFD0: Image file directory (main image)
ReadIFD(8);
// Parse IFD entries
i := 0;
while i < Length(FIFD) do begin
case FIFD[i].DataType of
1: w:=1; // unsigned byte
2: w:=1; // ascii string (terminated with 0)
3: w:=2; // unsigned short (2 bytes)
4: w:=4; // unsigned long (4 bytes)
5: w:=8; // unsigned rational (4+4 long)
else w:=1;
end;
c := w * FIFD[i].Count;
if c > 4 then begin
// Value contains offset from TIFF header to data
Stream.Position := 12 + Swap(FIFD[i].Value);
case FIFD[i].DataType of
2: begin
Dec(c);
SetLength(S, c);
Stream.Read(S[1], c);
end;
5: begin
Stream.Read(R, SizeOf(R));
D := Swap(R.numerator) / Swap(R.denominator);
end;
end;
end
else
case FIFD[i].DataType of
3: w := Swap(Word(FIFD[i].Value));
4: dw := Swap(FIFD[i].Value);
end;
case FIFD[i].TagNo of
// IFD0 Tags
$010F: FExif.Make := S;
$0110: FExif.Model := S;
$0112: FExif.Orientation := w;
$011A: FExif.XResolution := D;
$011B: FExif.YResolution := D;
$0128: FExif.ResolutionUnit := w;
$0131: FExif.Software := S;
$0132: FExif.DateTime := S;
$013B: FExif.Artist := S;
$8769: ReadIFD(dw); // offset to Exif SubIFD
// Exif SubIFD Tags
$829A: FExif.ExposureTime := D;
$829D: FExif.FNumber := D;
$A001: FExif.ColorSpace := w;
$A420: FExif.ImageUniqueID := S;
end;
Inc(i);
end;
end;
end;
function TJpegExifReader.Orientation: smallint;
begin
case FExif.Orientation of
3: Result := 180; // The 0th row is at the visual bottom of the image, and the 0th column is the visual right-hand side.
6: Result := 270; // The 0th row is the visual right-hand side of the image, and the 0th column is the visual top.
8: Result := 90; // The 0th row is the visual left-hand side of the image, and the 0th column is the visual bottom.
else Result := 0;
end;
end;
function TJpegExifReader.XResolution: double;
begin
Result := FExif.XResolution;
end;
function TJpegExifReader.YResolution: double;
begin
Result := FExif.YResolution;
end;
function TJpegExifReader.ResolutionUnit: string;
begin
case FExif.ResolutionUnit of
2: Result := 'in';
3: Result := 'cm';
else Result := '';
end;
end;
function TJpegExifReader.DateTime: TDateTime;
begin
if Length(FExif.DateTime) = 19 then
Result := ComposeDateTime(
StrToDate(Copy(FExif.DateTime,1,10), 'yyyy:mm:dd', ':'),
StrToTime(Copy(FExif.DateTime,12,8), ':')
)
else
Result := 0;
end;
end.