Getting the size of a GIF/JPG/PNG?
Hi!
I need code to get the size of an image in VB. I found similar code for Delphi, but haven't gotten around to converting it to VB - it uses some assembler code and
while delphi allows merging this code, VB doesn't. To make matters worse, I don't know Delphi that well.
Maybe there's a dynamic link library or ActiveX for these purposes?
Thanks a lot in advance!
Here's that weird code :-)
---
unit ImgSize; interface uses Classes; procedure GetJPGSize(const sFile: string; var wWidth, wHeight: word);
procedure GetPNGSize(const sFile: string; var wWidth, wHeight: word);
procedure GetGIFSize(const sGIFFile: string; var wWidth, wHeight: word); implementation uses SysUtils; function ReadMWord(f: TFileStream): word;
type
TMotorolaWord = record
case byte of
0: (Value: word);
1: (Byte1, Byte2: byte);
end;
var
MW: TMotorolaWord;
begin
{ It would probably be better to just read these two bytes in normally }
{ and then do a small ASM routine to swap them. But we aren't talking }
{ about reading entire files, so I doubt the performance gain would be }
{ worth the trouble. }
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) or (Seg = $C2) 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 := $FF; { Fake it to keep looping. }
end;
end;
end;
end;
finally
f.Free;
end;
end; procedure GetPNGSize(const sFile: string; var wWidth, wHeight: word);
type
TPNGSig = array[0..7] of byte;
const
ValidSig: TPNGSig = (137,80,78,71,13,10,26,10);
var
Sig: TPNGSig;
f: tFileStream;
x: integer;
begin
FillChar(Sig, SizeOf(Sig), #0);
f := TFileStream.Create(sFile, fmOpenRead);
try
f.Read(Sig[0], SizeOf(Sig));
for x := Low(Sig) to High(Sig) do
if Sig[x] <> ValidSig[x] then exit;
f.Seek(18, 0);
wWidth := ReadMWord(f);
f.Seek(22, 0);
wHeight := ReadMWord(f);
finally
f.Free;
end;
end; procedure GetGIFSize(const sGIFFile: string; var wWidth, wHeight: word);
type
TGIFHeader = packed record
Sig: array[0..5] of char;
ScreenWidth, ScreenHeight: word;
Flags, Background, Aspect: byte;
end; TGIFImageBlock = packed record
Left, Top, Width, Height: word;
Flags: byte;
end;
var
f: file;
Header: TGifHeader;
ImageBlock: TGifImageBlock;
nResult: integer;
x: integer;
c: char;
DimensionsFound: boolean;
begin
wWidth := 0;
wHeight := 0; if sGifFile = '' then
exit; {$I-}
FileMode := 0; { read-only }
AssignFile(f, sGifFile);
reset(f, 1);
if IOResult <> 0 then
{ Could not open file }
exit; { Read header and ensure valid file. }
BlockRead(f, Header, SizeOf(TGifHeader), nResult);
if (nResult <> SizeOf(TGifHeader)) or (IOResult <> 0) or
(StrLComp('GIF', Header.Sig, 3) <> 0) then
begin
{ Image file invalid }
close(f);
exit;
end; { Skip color map, if there is one }
if (Header.Flags and $80) > 0 then
begin
x := 3 * (1 SHL ((Header.Flags and 7) + 1));
Seek(f, FilePos(f) + x);
if IOResult <> 0 then
begin
{ Color map thrashed }
close(f);
exit;
end;
end; DimensionsFound := False;
FillChar(ImageBlock, SizeOf(TGIFImageBlock), #0);
{ Step through blocks. }
BlockRead(f, c, 1, nResult);
while (not EOF(f)) and (not DimensionsFound) do
begin
case c of
',': { Found image }
begin
BlockRead(f, ImageBlock, SizeOf(TGIFImageBlock), nResult);
if nResult <> SizeOf(TGIFImageBlock) then begin
{ Invalid image block encountered }
close(f);
exit;
end;
wWidth := ImageBlock.Width;
wHeight := ImageBlock.Height;
DimensionsFound := True;
end;
'?' : { Skip }
begin
{ NOP }
end;
{ nothing else. just ignore }
end;
BlockRead(f, c, 1, nResult);
end; close(f);
{$I+}
end; end.
