Seek a read TMemoryStream binary stream header files, to determine the sample code file type, thank you

CodePudding user response:

The following content is back, the image file header format:
1. The JPEG
- file header identifiers (2 bytes) : $ff, $d8 (SOI) (JPEG file id)
- end of file identifier (2 bytes) : $ff, $d9 (EOI)

2. The TGA
- 5 bytes uncompressed before 00 00 00 00 02
- before 5 bytes of RLE compression 10 00 00 00 00

3. The PNG
- file header identifiers (8 bytes) 50 89 e 47 0 d 0 a 1 a 0 a

4. GIF
47 - file head logo (6 bytes) 49 46 38 and 39 (37) 61
G I F 8 9 (7) a

5. BMP
- file head logo (2 bytes) 42 4 d
B M

6. The PCX
- file head logo (1 bytes) 0 a

7. TIFF
Mark - file header (2 bytes) 4 d, 4 d or 49 49

8. ICO
Mark - file header (8 bytes) 00 00 01 00 01 00 20 20

9. CUR
Mark - file header (8 bytes) 00 00 00 02 01 00 20 20

10. IFF
Mark - file header (4 bytes) 46 4 f and 4 d
F O R M

11. ANI
Mark - file header (4 bytes) 52 49 46 46
R I F F

 myimage.png:=TMemoryStream. Create; 
Myimage.png LoadFromFile (FileName);//put just the user to select the file is loaded into memory stream 
Myimage.png Position:=0;//move the pointer to the beginning place 
Myimage.png ReadBuffer (Buffer, 2);//read the file before 2 bytes, into the Buffer inside 
If Buffer=$4 d42 then//if the first two bytes are 4 d42/low to high (because memory is from high to low, from left to right in front of the so said BMP file header is $424 d, will in turn used to when compared with the data in the memory, compared with $4 d42 
The begin 
ShowMessage (' BMP);//this is BMP format files 
End 

CodePudding user response:

Want to see more of the contents of the file header, look at this website: http://www.garykessler.net/library/file_sigs.html

CodePudding user response:

This paper explained how to determine a real type of image files, not is judged by the suffix types of methods:

The following is a reference:

 unit Unit55; 

Interface 

USES the 
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms, 
Dialogs, StdCtrls; 

Type 
TImageType=(IT_None, IT_Error IT_Bmp, IT_JPEG, IT_GIF, IT_PCX, IT_PNG, 
IT_PSD IT_RAS, IT_SGI IT_TIFF); 

TForm55=class (TForm) 
OpenDialog1: TOpenDialog; 
For: TButton; 
Procedure Button1Click (Sender: TObject); 
Private 
{Private declarations} 
Public 
{Public declarations} 
end; 

Var 
Form55: TForm55; 

Implementation 

{$R *. DFM} 

The function CheckImageType (FileName: string) : TImageType; 
Var 
Myimage.png: TMemoryStream; 
Buffer: Word; 
The begin 
Myimage.png:=TMemoryStream. Create; 
Try 
Myimage.png LoadFromFile (FileName); 
Myimage.png Position:=0; 
If myimage.png Size=0 then//if the file Size is equal to zero, then the error (
The begin 
Result:=IT_Error; 
The Exit; 
end; 
Myimage.png ReadBuffer (Buffer, 2);//read the file before 2 bytes, into the Buffer inside 

Case Buffer of 
$4 d42: 
Result:=IT_Bmp; 
$D8FF: 
Result:=IT_JPEG; 
$4947: 
Result:=IT_GIF; 
A: $050 
Result:=IT_PCX; 
$5089: 
Result:=IT_PNG; 
$4238: 
Result:=IT_PSD; 
$A659: 
Result:=IT_RAS; 
$DA01: 
Result:=IT_SGI; 
$4949: 
Result:=IT_TIFF; 
The else 
Result:=IT_None; 
end; 
The finally 
Myimage.png Free; 
end; 
end; 

Procedure TForm55. Button1Click (Sender: TObject); 
The begin 
If not OpenDialog1. Execute then 
The Exit; 
If CheckImageType (OpenDialog1 FileName) & lt;> IT_Bmp then 
Showmessage (' is not a BMP format); 

end; 

End.