Obtain the image size of an image file

// ================================================ ====================================
// Function: of_getpicturesize ()
//--------------------------------------------------------------------
// Description: obtains the image size of an image file (supported in GIF, JPG, and BMP formats)
//--------------------------------------------------------------------
// Parameters:
// Value string as_filename name of the image file
// Reference long al_picturewidth returns the Image Width
// Reference long al_pictureheight returns the Image Height
//--------------------------------------------------------------------
// Return value: integer 1-success, 0-Failure
//--------------------------------------------------------------------

Integer li_file, li_dataread
Blob lb_data
Long ll_filelength, ll_picturewidth, ll_pictureheight
Long ll_datalen, ll_datapos, ll_filepos
Boolean lb_loopflag = true
Char lc_char1, lc_char2

// The file does not exist.
If not fileexists (as_filename) then return 0

// Obtain the file size
Ll_filelength = filelength (as_filename)

// Open the file
Li_file = fileopen (as_filename, streammode !)
If li_file =-1 then return 0

// Read the file
Li_dataread = fileread (li_file, lb_data)
If li_dataread <= 0 then
Fileclose (li_file)
Return 0
End if

// Currently, there are two main types of GIF
// 1. It is identified as gif87a and is only used to store a single static image.
// 2. Marked as gif89a. Several static images can be stored at the same time to form continuous animation.
// The first 6 bytes of the file are marked as: gif87a or gif89a, and the 7 or 8 bytes are the image width (width ),
// The 9th and 10th bytes are the height of the image. Pay attention to the two bytes before the low position

// Determine the GIF File Format
If string (blobmid (lb_data,) = 'gif 8' then
Ll_picturewidth = ASC (string (blobmid (lb_data, 7,1) + ASC (string (blobmid (lb_data, 8, 1 )))*

256
Ll_pictureheight = ASC (string (blobmid (lb_data, 9, 1) + ASC (string (blobmid (lb_data, 10, 1 )))

* 256
If ll_picturewidth> 0 and ll_pictureheight> 0 then
Al_picturewidth = ll_picturewidth
Al_pictureheight = ll_pictureheight
Fileclose (li_file)
Return 1
Else
Fileclose (li_file)
Return 0
End if
End if

// JPEG file format
// The first three bytes are marked as 0xff, 0xd8, and 0xff.
If string (blobmid (lb_data, 255) = char (216) + char (255) + char () then
Ll_datalen = Len (lb_data)
Ll_datapos = 3
Ll_filepos = 3
Do While lb_loopflag
Ll_datapos = ll_datapos + 1
Ll_filepos = ll_filepos + 1
Lc_char1 = string (blobmid (lb_data, ll_datapos, 1 ))
Lc_char2 = string (blobmid (lb_data, ll_datapos + 1,1 ))
If lc_char1 = char (255) and lc_char2 <> char (255) then
If lc_char2> = char (192) and lc_char2 <= char (195) then
// Locate the Dimension Data
Ll_picturewidth = ASC (string (blobmid (lb_data, ll_datapos + 7,1 )))*

256 + ASC (string (blobmid (lb_data, ll_datapos + 8, 1 )))
Ll_pictureheight = ASC (string (blobmid (lb_data, ll_datapos + 5, 1 )))

* 256 + ASC (string (blobmid (lb_data, ll_datapos + 6, 1 )))
Lb_loopflag = false
Else
// No size data is found and the file is read again
Ll_filepos = ll_filepos + ASC (string (blobmid (lb_data, ll_datapos +

3, 1) * 256 + ASC (string (blobmid (lb_data, ll_datapos +) + 1
If ll_filepos> ll_filelength then
Fileclose (li_file)
Return 0
Else
FileSeek (li_file, ll_filepos)
Fileread (li_file, lb_data)
Ll_datalen = Len (lb_data)
Ll_datapos = 0
End if
End if
End if
If ll_datapos = ll_datalen-9 and lb_loopflag = true then
Ll_filepos = ll_filepos-9
FileSeek (li_file, ll_filepos)
Fileread (li_file, lb_data)
Ll_datalen = Len (lb_data)
Ll_datapos = 0
End if
If ll_filepos> = ll_filelength then
Lb_loopflag = false
End if
Loop
If ll_picturewidth> 0 and ll_pictureheight> 0 then
Al_picturewidth = ll_picturewidth
Al_pictureheight = ll_pictureheight
Fileclose (li_file)
Return 1
Else
Fileclose (li_file)
Return 0
End if
End if

// BMP file format
// The first two bytes are identifiers: there may be many types of identifiers
// The 19,20, bytes are the width (width), 25, and 26 bytes are the height (height)
// DWORD is composed of four bytes.
If string (blobmid (lb_data, 1, 2) = 'bm 'then
Ll_picturewidth = ASC (string (blobmid (lb_data, 19,1) + ASC (string (blobmid (lb_data, 20,1 )))

* 256 + ASC (string (blobmid (lb_data, 21,1) * 65536 + ASC (string (blobmid (lb_data, 16777216) *
Ll_pictureheight = ASC (string (blobmid (lb_data,) + ASC (string (blobmid (lb_data, 24, 1 )))

* 256 + ASC (string (blobmid (lb_data, 65536) * 16777216 + ASC (string (blobmid (lb_data ,) *
If ll_picturewidth> 0 and ll_pictureheight> 0 then
Al_picturewidth = ll_picturewidth
Al_pictureheight = ll_pictureheight
//// Convert the actual image size to the pbunit size and return
// Al_picturewidth = pixelstounits (ll_picturewidth, xpixelstounits !)
// Al_pictureheight = pixelstounits (ll_pictureheight, ypixelstounits !)
Fileclose (li_file)
Return 1
Else
Fileclose (li_file)
Return 0
End if
End if

Return 0