There are occasions in which I need (or want) to make screenshots when I'm watsching a movie with the 'xine' media player. Xine always makes PNG files but some of my applications require the pictures to be JPG and minimum dimensions of 400 pixels on either side. So I used to run the command:

    convert -resize 150% shot-1.png AA-1.jpg
and for a few screenshots that was enough. Lster, when more screenshots were required, the command line version was too time consuming. So I made a file called 'go' and in it were sets of lines like the one above. That worked,, but making the batch files was a lot of work. So I decided to automate it: make the batch files automatically, make the resultant file executable and start it. And it works!

conv: make a batchfile to convert images

Below is the source. It is an easy program. There are just a few things which are special:

What it comes down to:
  1. Get the name of the PNG files (old prefix)
  2. Get the name for the JPG files (new prefix)
  3. Get the range of the pictures
  4. Get the scal factor for '-resize'
  5. Enter a LOOP to create thje conversion commands
  6. Close all files
  7. Return to the command shell
And that's just about it!

The format of the input files is as follows: MyMovie-xxx.png where

Text Purpose
MyMovie The name of the movie being played by Xine when the screenshot was made
- Introduced by Xine to separate moviename from serial number
xxx Serial number (auto incremented) by Xine

Xine numbers the files it creates without leading zero's. The new JPG files need trailing zero's for easier uploading to photo album sites.

The source

Below is the source. The InOut.WriteBf commands were needed since Linux does not print messages on screen before a LineFeed is encountered. For the rest it is all very straight forward.

MODULE conv;

IMPORT  InOut, Strings, NumConv, TextIO;

TYPE 	Identifier		= ARRAY [0..31] OF CHAR;

VAR	old, new, factor	: Identifier;
	line 			: ARRAY [0..63] OF CHAR;
	from, until, nr		: CARDINAL;
	tmp   			: ARRAY [0..7] OF CHAR;
	ok			: BOOLEAN;
	file			: TextIO.File;

   InOut.WriteString ("Old prefix    : ");	InOut.WriteBf;
   InOut.ReadString (old);

   InOut.WriteString ("New prefix    : ");	InOut.WriteBf;
   InOut.ReadString (new);

   InOut.WriteString ("From nr       : ");	InOut.WriteBf;
   InOut.ReadCard (from);
   InOut.WriteString ("Until nr      : ");	InOut.WriteBf;
   InOut.ReadCard (until);
   InOut.WriteString ("Resize factor : ");	InOut.WriteBf;
   InOut.ReadString (factor);
   nr := from;
   TextIO.OpenOutput (file, "go");

      line := "convert ";
      IF  factor [0] # '-'  THEN
         Strings.Append (line, "-resize ");
	 Strings.Append (line, factor);
	 Strings.Append (line, "% ")
      Strings.Append (line, old);	Strings.Append (line, "-");
      NumConv.Num2Str (nr, 10, tmp, ok);
      Strings.Append (line, tmp);	Strings.Append (line, ".png ");
      Strings.Append (line, new);	Strings.Append (line, "-");
      NumConv.AdjustWidth (tmp, 3, "0");
      Strings.Append (line, tmp);	Strings.Append (line, ".jpg");
      TextIO.PutString (file, line);	TextIO.PutLn (file);
      INC (nr);
      IF  nr > until  THEN  EXIT  END
   TextIO.PutLn (file);
   TextIO.Close (file);
   InOut.WriteString ("Done");		InOut.WriteLn
END conv.

What it does

Below is an example of the use of the conv program:

   -$ ls
   GBG11-1.png  GBG11-2.png  GBG11-3.png  GBG11-4.png  GBG11-5.png  GBG11-6.png
   -$ conv
   Old prefix    : GBG11
   New prefix    : AZ
   From nr       : 1
   Until nr      : 6
   Resize factor : 125
   -$ cat go
   convert -resize 125% GBG11-1.png AZ-001.jpg
   convert -resize 125% GBG11-2.png AZ-002.jpg
   convert -resize 125% GBG11-3.png AZ-003.jpg
   convert -resize 125% GBG11-4.png AZ-004.jpg
   convert -resize 125% GBG11-5.png AZ-005.jpg
   convert -resize 125% GBG11-6.png AZ-006.jpg
   -$ chmod 700 go
   -$ ./go
   -$ ls -lh
   total 3.8M
   -rw-r--r--  1 jan users  57K 2007-06-12 16:54 AZ-001.jpg
   -rw-r--r--  1 jan users  57K 2007-06-12 16:54 AZ-002.jpg
   -rw-r--r--  1 jan users  57K 2007-06-12 16:54 AZ-003.jpg
   -rw-r--r--  1 jan users  48K 2007-06-12 16:54 AZ-004.jpg
   -rw-r--r--  1 jan users  42K 2007-06-12 16:54 AZ-005.jpg
   -rw-r--r--  1 jan users  54K 2007-06-12 16:54 AZ-006.jpg
   -rw-r--r--  1 jan users 610K 2007-06-12 16:48 GBG11-1.png
   -rw-r--r--  1 jan users 612K 2007-06-12 16:48 GBG11-2.png
   -rw-r--r--  1 jan users 608K 2007-06-12 16:48 GBG11-3.png
   -rw-r--r--  1 jan users 519K 2007-06-12 16:48 GBG11-4.png
   -rw-r--r--  1 jan users 508K 2007-06-12 16:48 GBG11-5.png
   -rw-r--r--  1 jan users 601K 2007-06-12 16:48 GBG11-6.png
   -rwx------  1 jan users  265 2007-06-12 16:48 go
After the 'go' command the processor is quite busy. But it is the fastest way to do these things. See if you can use the program for your purposes, probably after you made massive changes.
As you can see, the JPG files may be 25% bigger, yet they are 90% smaller!

Page created 12 June 2007,

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