Help translating fread to substr

[RootShell]

Dear All

Im having some dificulty here:

I found a great PHP code by Catalin Mihaila that reads a SRC (Sinclair
Spectrum $SCREEN Image Format) and tranforms it into PNG format to show
onscreen by the PHP gd2 Library.

The problem is that im trying to translate the 'fread' structure into a
MySQL blob reading, as follows:

Original file access code:

$zxscr = fread($handle, 6144); // first 6144 bytes of file
$attrs = fread($handle, 768); // last 768 bytes of file

My actual MySQL access code:

$zxscr = substr($row[Image], 0, 6144); // first 6144 bytes
of MySQL field "Imagem" inside table "Perguntas"
$attrs = substr($row[Image], -768); // last 768 bytes of
MySQL field "Imagem" inside table "Perguntas"

Here's the original full CODE (for reading the file from servers directory):

$filename=$_GET['scrimg'];
if(!$filename) error("Invalid filename");
$handle = fopen($filename, "r");
if(filesize($filename)<>6912) { fclose($handle); error("Size
of file must be 6912 bytes"); }
$zxscr = fread($handle, 6144); // first 6144 bytes of file
$attrs = fread($handle, 768); // last 768 bytes of file
fclose($handle);

And here's what i changed it into (for reading from a blob field inside
MySQL db):

mysql_connect("localhost", "user", "password") or die("Could
not connect: " . mysql_error());
mysql_select_db("jb-ntg");
$result = mysql_query("SELECT Numero, Nome, Imagem FROM
Perguntas WHERE Numero = jogo");
$zxscr = substr($row[Image], 0, 6144); // first 6144 bytes
of MySQL field "Imagem" inside table "Perguntas"
$attrs = substr($row[Image], -768); // last 768 bytes of
MySQL field "Imagem" inside table "Perguntas"

Here's the structure of the DB "jb-ntg"

CREATE TABLE `perguntas` (
`Numero` int(11) NOT NULL auto_increment,
`Nome` mediumtext NOT NULL,
`Imagem` blob NOT NULL,
`Acessos` int(11) NOT NULL default '0',
`Certas` int(11) NOT NULL default '0',
PRIMARY KEY (`Numero`)
) TYPE=MyISAM AUTO_INCREMENT=3 ;

But i get a blank image (with the right dimensions, so the script must be
ok) the only problem i think is the fact that in the original code i could
get the first 6144 bytes and last 768 bytes of the file, but using the MySQL
blob i apparently cant at least using the substr, and i sincerely have no
idea of the binary equivalent of the fread for blob files.

Anyone can help?

I never coded in PHP and this is my first try at this new language, as you
should remember im trying to make a "Name the Game" PHP game devoted to ZX
Spectrum, and i will, i just need a few guiding lines over here and there.

Thanks for any support in advance,
RootShell

[Pedro Graca]

RootShell wrote:

(snipped)

And here's what i changed it into (for reading from a blob field inside
MySQL db):

mysql_connect("localhost", "user", "password") or die("Could
not connect: " . mysql_error());
mysql_select_db("jb-ntg");
$result = mysql_query("SELECT Numero, Nome, Imagem FROM
Perguntas WHERE Numero = jogo");

$result is a resource "pointing" to a set of rows.
You're not using this resource in your code.

You need to do

$row = mysql_fetch_assoc($result);

to fill $row with data from the database.

$zxscr = substr($row[Image], 0, 6144); // first 6144 bytes
of MySQL field "Imagem" inside table "Perguntas"

$row[Image] (probably you mean $row["Imagem"], right?) has not been
filled with data from the database;
so now the value of $zxscr is the empty string.

$attrs = substr($row[Image], -768); // last 768 bytes of
MySQL field "Imagem" inside table "Perguntas"

$attrs = '';

Here's the structure of the DB "jb-ntg" (snipped) But i get a blank image (with the right dimensions, so the script must be
ok)

Maybe the right dimensions come from your HTML tags?
<img src="whatever" width="80" height="24" alt="ZX Spectrum screen shot"/>
the only problem i think is the fact that in the original code i could
get the first 6144 bytes and last 768 bytes of the file, but using the MySQL
blob i apparently cant at least using the substr, and i sincerely have no
idea of the binary equivalent of the fread for blob files.

Anyone can help?

I never coded in PHP and this is my first try at this new language, as you
should remember im trying to make a "Name the Game" PHP game devoted to ZX
Spectrum, and i will, i just need a few guiding lines over here and there.

Bem vindo ao PHP e boa-noite :)

[Translation: welcome to PHP and good night :)]

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[R. Rajesh Jeba Anbiah]

"RootShell" <ro*******@netcabo.pt> wrote in message news:<40**********************@news.telepac.pt>...

Dear All

Im having some dificulty here:

I found a great PHP code by Catalin Mihaila that reads a SRC (Sinclair
Spectrum $SCREEN Image Format) and tranforms it into PNG format to show
onscreen by the PHP gd2 Library.

The problem is that im trying to translate the 'fread' structure into a
MySQL blob reading, as follows:

<snip>

Not a direct answer to your question...

If you want to read the header info from the file use unpack()
<http://in2.php.net/unpack>

A good example is found at
<http://fooassociates.com/phpfer/html/rn45re878.html> and it was
suggested as a nice workaround for "struct" (C's) by Andy and Chung.
--
| Just another PHP saint |
Email: rrjanbiah-at-Y!com