Getting picture width and height without LCL
lazarus / 39-Graphics

----------------------------------------------------------------------
wp · 2016-03-01 22:25

For image support in fpspreadsheet I need to know the pixel width and
height of pictures. Since the basic fpspreadsheet units do not use the
LCL I am not allowed to apply the Graphics unit. What is the best way
to determine these quantities based on non-LCL procedures for the
typical graphics formats?

----------------------------------------------------------------------
Jurassic Pork · 2016-03-02 00:54

hello,
maybe you can use the fpimage and the fpreadxxx  (ex: fpreadpng )
units.
Example to read the height and width of a png picture :
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i Uses
 fpreadpng, fpimage;var  image: TFPCustomImage;  reader:
TFPCustomImageReader;begin  Image := TFPMemoryImage.Create(10,10); 
Reader := TFPReaderPNG.Create; 
Image.LoadFromFile('F:\temp\images\1111.png', Reader);  Writeln(
'image Width : ' + InttoStr(Image.Width) +           ' - image Height
: ' + InttoStr(Image.Height) );  Readln;  Image.Free;  Reader.Free;
end. 
Friendly, J.P

----------------------------------------------------------------------
engkin · 2016-03-02 03:57

There is another version of LoadFromFile that recognizes image types
that were added to the ImageHandlers (this happened in the
initialization section of every FPReadXXX unit):
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i program
Project1; Uses  sysutils, fpimage, fpreadbmp, fpreadjpeg, fpreadpng
{... find the rest in fpc\3.0.0\source\packages\fcl-image\src
folder}; var  image: TFPCustomImage;begin  Image :=
TFPMemoryImage.Create(10,10); 
Image.LoadFromFile('YourImageFileName<===');  Writeln( 'image Width :
' + InttoStr(Image.Width) +           ' - image Height : ' +
InttoStr(Image.Height) );  Image.Free;  Readln;end.

----------------------------------------------------------------------
wp · 2016-03-02 06:17

Ah, thank you. I had seen this before but was confused because the
FPCustomImage dimensions must be specified in the constructor.

Next question: How to get the pixel density (dpi)? This would allow to
specify the 100%-size of the image.

----------------------------------------------------------------------
Bart · 2016-03-02 16:25

http://svn.code.sf.net/p/flyingsheep/code/trunk/MijnLib/picslib.pp.
Provides:
Code: [Select]type
  TImageFormat = (ifUnknown, ifBmp, ifPng, ifGif, ifJpg);

function GetImageSize(const Fn: String; out Width, Height: dword):
Boolean;
function GetImageSizeAndFormat(const Fn: String; out Width, Height:
dword): TImageFormat;

Bart

----------------------------------------------------------------------
wp · 2016-03-02 17:12

Bart, thanks for sharing. In fact, I've set up something similar in
the meantime. Because FPCustomImage does not return the dpi values I
have to read the jpeg and bmp headers like you do - and it has the
advantage that the entire image machinery is kept out of
fpspreadsheet. Would you allow me to copy some snippets over to the
new fpspreadsheet unit fpsimages?

----------------------------------------------------------------------
Bart · 2016-03-02 17:55

Quote from: wp on March 02, 2016, 06:12:22 pmBart, thanks for
sharing.  ....
Would you allow me to copy some snippets over to the new fpspreadsheet
unit fpsimages?

It's LGPL, so be my guest.

Bart

----------------------------------------------------------------------
wp · 2016-03-03 19:31

Bart, as a "guest present" I am donating my function how to get image
size (and dpi - but this is not in your lib) from TIFF files, you may
have to edit it a bit to fit it into your lib:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i type 
TByteOrder = (boLE, boBE);  // little edian, or big endian { Makes
sure that the byte order of w is the same as specified by the
parameter }function FixByteOrder(w: Word; AByteOrder: TByteOrder):
Word; overload;begin  Result := IfThen(AByteOrder = boLE, LEToN(w),
BEToN(w));end; { Makes sure that the byte order of dw is the same as
specified by the parameter }function FixByteOrder(dw: DWord;
AByteOrder: TByteOrder): DWord; overload;begin  Result :=
IfThen(AByteOrder = boLE, LEToN(dw), BEToN(dw));end; function
GetTIFSize(AStream: TStream; out AWidth, AHeight: DWord;  out dpiX,
dpiY: Double): Boolean;type  TTifHeader = packed record     BOM: word;
    // 'II' for little endian, 'MM' for big endian     Sig: word;    
// Signature (42)     IFD: DWORD;    // Offset where image data begin 
end;  TIFD_Field = packed record    Tag: word;    FieldType: word;   
ValCount: DWord;    ValOffset: DWord;  end;var  header: TTifHeader =
(BOM:0; Sig:0; IFD:0);  dirEntries: Word;  field: TIFD_Field = (Tag:0;
FieldType:0; ValCount:0; ValOffset:0);  i: Integer;  bo: TByteOrder; 
num, denom: LongInt;  units: Word;  p, pStart: Int64;begin  Result :=
false;  AWidth := 0;  AHeight := 0;  dpiX := 0;  dpiY := 0;  units :=
0;   // Remember current stream position because procedure is called
also from  // jpeg Exif block.  pStart := AStream.Position;   if
AStream.Read(header, SizeOf(TTifHeader)) < SizeOf(TTifHeader) then
exit;  if not ((header.BOM = $4949) or (header.BOM = $4D4D)) then
exit;  if header.BOM = $4949 then bo := boLE else bo := boBE; // 'II'
--> little endian, 'MM' --> big endian  if FixByteOrder(header.Sig,
bo) <> 42 then exit;   AStream.Position := pStart +
FixByteOrder(header.IFD, bo);  dirEntries :=
FixByteOrder(AStream.ReadWord, bo);  for i := 1 to dirEntries do 
begin    AStream.Read(field, SizeOf(field));    field.Tag :=
FixByteOrder(field.Tag, bo);    field.ValOffset :=
FixByteOrder(field.ValOffset, bo);    field.FieldType :=
FixByteOrder(field.FieldType, bo);    p := AStream.Position;    case
field.Tag OF      $0100 : AWidth := field.ValOffset;      $0101 :
AHeight := field.ValOffset;      $011A : begin    // XResolution as
RATIONAL value                AStream.Position := pStart +
field.ValOffset;                num := FixByteOrder(AStream.ReadDWord,
bo);                denom := FixByteOrder(AStream.ReadDWord, bo);    
          dpiX := num/denom;              end;      $011B : begin  
 // YResolution as RATIONAL value                AStream.Position :=
pStart + field.ValOffset;                num :=
FixByteOrder(AStream.ReadDWord, bo);                denom :=
FixByteOrder(AStream.ReadDWord, bo);                dpiY :=
num/denom;              end;      $0128 : begin                units
:= field.ValOffset;   // 1: non-square 2: inches, 3: cm             
end;    end;    if (AWidth > 0) and (AHeight > 0) and (dpiX > 0) and
(dpiY > 0) and (units > 0)    then      break;    AStream.Position :=
p;  end;   case units of    1: begin dpiX := 96; dpiY := 96; end;   
2: ;  // is already inches, nothing to do    3: begin dpiX := dpiX *
2.54; dpiY := dpiY * 2.54; end;  end;   Result := true;end;

----------------------------------------------------------------------
Bart · 2016-03-03 23:52

Quote from: wp on March 03, 2016, 08:31:22 pmBart, as a "guest
present" I am donating my function how to get image size (and dpi -
but this is not in your lib) from TIFF files, you may have to edit it
a bit to fit it into your lib:

Thanks, I'll look into it.
Do the other filetypes have DPI info as well, and do you have code to
extract that?

Bart

----------------------------------------------------------------------
wp · 2016-03-04 00:21

Yes. You can have a look at it, it's all online now in fpspreadsheet's
fpsimages (https://sourceforge.net/p/lazarus-
ccr/svn/HEAD/tree/components/fpspreadsheet/fpsimages.pas). You can
remove the dependence on fpsutils which brings in just some length
unit conversion needed for svg (which does not have a true dpi
either).

----------------------------------------------------------------------
Bart · 2024-01-07 00:15

Quote from: wp on March 03, 2016, 08:31:22 pmBart, as a "guest
present" I am donating my function how to get image size (and dpi -
but this is not in your lib) from TIFF files, you may have to edit it
a bit to fit it into your lib:

Integrated into my picslib unit.
Took me just shy of 8 years  

Thanks.