Mega Code Archive
Get width and height of a JPEG image file
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Title: Get width and height of a JPEG image file
function ReadMWord(f: TFileStream): Word;
type
TMotorolaWord = record
case Byte of
0: (Value: Word);
1: (Byte1, Byte2: Byte);
end;
var
MW: TMotorolaWord;
begin
f.read(MW.Byte2, SizeOf(Byte));
f.read(MW.Byte1, SizeOf(Byte));
Result := MW.Value;
end;
procedure GetJPGSize(const sFile: string; var wWidth, wHeight: Word);
const
ValidSig: array[0..1] of Byte = ($FF, $D8);
Parameterless = [$01, $D0, $D1, $D2, $D3, $D4, $D5, $D6, $D7];
var
Sig: array[0..1] of byte;
f: TFileStream;
x: integer;
Seg: byte;
Dummy: array[0..15] of byte;
Len: word;
ReadLen: LongInt;
begin
FillChar(Sig, SizeOf(Sig), #0);
f := TFileStream.Create(sFile, fmOpenRead);
try
ReadLen := f.read(Sig[0], SizeOf(Sig));
for x := Low(Sig) to High(Sig) do
if Sig[x] ValidSig[x] then ReadLen := 0;
if ReadLen 0 then
begin
ReadLen := f.read(Seg, 1);
while (Seg = $FF) and (ReadLen 0) do
begin
ReadLen := f.read(Seg, 1);
if Seg $FF then
begin
if (Seg = $C0) or (Seg = $C1) then
begin
ReadLen := f.read(Dummy[0], 3); { don't need these bytes }
wHeight := ReadMWord(f);
wWidth := ReadMWord(f);
end
else
begin
if not (Seg in Parameterless) then
begin
Len := ReadMWord(f);
f.Seek(Len - 2, 1);
f.read(Seg, 1);
end
else
Seg := $FF; { Fake it to keep looping. }
end;
end;
end;
end;
finally
f.Free;
end;
end;
Example usage:
var width,height:word;
begin
GetJPGSize(filename,width, height);
end;
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