PHP - Convert single byte to Integer (PCX Graphic Format)

Question

I'm working on a project that involves talking directly with Zebra printers. Currently, I am trying to convert images to the GRF format using something called "ztools". ZTools appears to be ancient and doesn't always convert the graphic correctly.

I've began digging up information on the PCX file format it is converting from and now find myself in byte land. This is my reference at this time: PCX Technical Reference

So, I have a basic PCX file I saved from photoshop that is 2x2 and would look like this:

10
01

This is where I am stuck, however. I've never worked with bytes and am attempting to read the pcx file with PHP using fopen("file", "rb"); and fread. However, it seems no matter what I do, I get a bunch of zeros. Anyone know what I need to do to convert the bytes to there numeric equivalents?

This is my weak attempt:

<?php
$file = "test.pcx";

// Open the file for binary reading (b flag)
$handle = fopen($file, "rb");

while (!feof($handle)) {
    $contents = fread($handle, 1);
    $contents = $contents >> 8;
    echo $contents >> 8;
    $content .= $contents;
}


fclose($handle);

Do you know php functions `pack` and `unpack`? I believe they're what you're looking for. — Vyktor, Feb 20 '12 at 14:48

score 3 · Accepted Answer · answered Feb 20 '12 at 15:59

I was able to get the header information accurately with this:

<?php
$file = "test.pcx";

function intToBits($int) {
    $return = "00000000";
    if ($int <= 255 && $int >= 0) {
        $check = 128;
        $x = 0;
        while ($int > 0) {
            if ($int > $check) {
                $return[$x] = "1";
            }
            $int -= $check;
            $check /= 2;
            $x++;
        }
    }
    return $return;
}

// Open the file for binary reading (b flag)
$handle = fopen($file, "rb");
$PCX_MAP = array();
$PCX_MAP['Manufacturer'][0] = 1; // Manufacturer
$PCX_MAP['Version'] = 1; // Version Info
$PCX_MAP['Encoding'] = 1; // Encoding
$PCX_MAP['BitsPerPixel'] = 1; // BitsPerPixel
$PCX_MAP['Xmin'] = 2; // Window Xmin
$PCX_MAP['Ymin'] = 2; // Window Ymin
$PCX_MAP['Xmax'] = 2; // Window Xmax
$PCX_MAP['Ymax'] = 2; // Window Ymax
$PCX_MAP['HDpi'] = 2; // HDpi (Resolution)
$PCX_MAP['VDpi'] = 2; // VDpi (Resolution)
$PCX_MAP['colormap'] = 48; // Colormap
$PCX_MAP['Reserved'] = 1; // Reserved = 0
$PCX_MAP['NumberColorPlanes'] = 1; // Number of color planes
$PCX_MAP['BytesPerLine'] = 2; // Bytes Per Line
$PCX_MAP['PalleteInfo'] = 2; // Palette Info
$PCX_MAP['HorizontalScreenSize'] = 2; // H Screen Size
$PCX_MAP['VerticalScreenSize'] = 2; // V Screen Size
$PCX_MAP['Filler'] = 54; // Filler

$length = reset($PCX_MAP);
while (!feof($handle)) {
    if ($length !== false) {
        $contents = fread($handle, $length);
        $contents = ord($contents);
        echo key($PCX_MAP) . " : {$contents}\n";
        $content .= $contents;
        $length = next($PCX_MAP);
    }
    else {
        // Get the rest 1 By 1
        $contents = fread($handle, 1);
        $contents = ord($contents);
        $contents = intToBits($contents);
        echo $contents ."\n";
    }
}


fclose($handle);
/*
$data = file_get_contents($file);

for($i = 0; $i < strlen($data); ++$i) {
    $char = ord($data[$i]);
    echo "Byte $i: $char\n";
}*/

However, I am still attempting to parse the image data.

This currently returns this:

Manufacturer : 10
Version : 5
Encoding : 1
BitsPerPixel : 1
Xmin : 0
Ymin : 0
Xmax : 3
Ymax : 1
HDpi : 200
VDpi : 200
colormap : 15
Reserved : 0
NumberColorPlanes : 1
BytesPerLine : 2
PalleteInfo : 1
HorizontalScreenSize : 0
VerticalScreenSize : 0
Filler : 0
10000000
11000000
11111110
00000000
11000000
11111110
00000000

The header information is correct, but I'm not sure about the data after filler.

The graphic ran in this instance is a 4 x 2 - 0 means white, 1 means black

0101
1010

score 1 · Answer 2 · answered Feb 20 '12 at 14:51

1

Try this:

while (!feof($handle)) {
    $contents = fread($handle, 1);
    $contents = $contents && 0xFF;
    echo $contents;
    $content .= $contents;
}

answered Feb 20 '12 at 14:51

oktawian

26
3

oktawian: I tried that and it returned all 1's. However, I was able to read 1 byte at a time and use ord to convert it to the integer value of the ascii character. Now my problem is parsing the data of the image. (I have the header, but understanding the actual image data has me baffled at the moment.) – teynon Feb 20 '12 at 15:58

PHP - Convert single byte to Integer (PCX Graphic Format)

2 Answers2