imagecreatefromwbmp

php at webdecker dot de (2010-01-28 03:05:33)

To get the horizontal and vertical resolution you could add some lines to the previous code of alexander. BMP stores the resolution in pixels per meter. To get it as pixels per inch (dpi) you have to multiply the value by 0.0254.

<?php
    public function imagecreatefrombmp($p_sFile)
    {
            // ...
            // ... insert after the lines where you get width and height...

            //    Get the horz. resolution in pixel per meter, 4 bytes
            $dpix = hexdec($header_parts[39]. $header_parts[38]) * 0.0254;
            
            //    Get the vert. resolution in pixel per meter, 4 bytes
            $dpiy = hexdec($header_parts[43]. $header_parts[42]) * 0.0254;

            // ... rest of the code...

            return ($image, $dpix, $dpiy);
    }           
?>

alexander at alexauto dot nl (2008-10-08 04:59:12)

AeroX created a nice example, but it only works at specific imagesizes because bmp uses fully 32-bit lines. To prevent failures (different colors, pixel-shifting per line), the solution is to skip the padding, inserted after color-pixels on the line. His implementation did cutting the padding into the image-data, causing wrong colors, pixel-shifting per line and also an large memory-consumption.

I improved this script to the next implementation. The readability of a image is checked by a other function, so it doesn't take part in this script.
Suggestions? Please let me know.

<?php
    public function imagecreatefrombmp($p_sFile)
    {
        //    Load the image into a string
        $file    =    fopen($p_sFile,"rb");
        $read    =    fread($file,10);
        while(!feof($file)&&($read<>""))
            $read    .=    fread($file,1024);
        
        $temp    =    unpack("H*",$read);
        $hex    =    $temp[1];
        $header    =    substr($hex,0,108);
        
        //    Process the header
        //    Structure: http://www.fastgraph.com/help/bmp_header_format.html
        if (substr($header,0,4)=="424d")
        {
            //    Cut it in parts of 2 bytes
            $header_parts    =    str_split($header,2);
            
            //    Get the width        4 bytes
            $width            =    hexdec($header_parts[19].$header_parts[18]);
            
            //    Get the height        4 bytes
            $height            =    hexdec($header_parts[23].$header_parts[22]);
            
            //    Unset the header params
            unset($header_parts);
        }
        
        //    Define starting X and Y
        $x                =    0;
        $y                =    1;
        
        //    Create newimage
        $image            =    imagecreatetruecolor($width,$height);
        
        //    Grab the body from the image
        $body            =    substr($hex,108);

        //    Calculate if padding at the end-line is needed
        //    Divided by two to keep overview.
        //    1 byte = 2 HEX-chars
        $body_size        =    (strlen($body)/2);
        $header_size    =    ($width*$height);

        //    Use end-line padding? Only when needed
        $usePadding        =    ($body_size>($header_size*3)+4);
        
        //    Using a for-loop with index-calculation instaid of str_split to avoid large memory consumption
        //    Calculate the next DWORD-position in the body
        for ($i=0;$i<$body_size;$i+=3)
        {
            //    Calculate line-ending and padding
            if ($x>=$width)
            {
                //    If padding needed, ignore image-padding
                //    Shift i to the ending of the current 32-bit-block
                if ($usePadding)
                    $i    +=    $width%4;
                
                //    Reset horizontal position
                $x    =    0;
                
                //    Raise the height-position (bottom-up)
                $y++;
                
                //    Reached the image-height? Break the for-loop
                if ($y>$height)
                    break;
            }
            
            //    Calculation of the RGB-pixel (defined as BGR in image-data)
            //    Define $i_pos as absolute position in the body
            $i_pos    =    $i*2;
            $r        =    hexdec($body[$i_pos+4].$body[$i_pos+5]);
            $g        =    hexdec($body[$i_pos+2].$body[$i_pos+3]);
            $b        =    hexdec($body[$i_pos].$body[$i_pos+1]);
            
            //    Calculate and draw the pixel
            $color    =    imagecolorallocate($image,$r,$g,$b);
            imagesetpixel($image,$x,$height-$y,$color);
            
            //    Raise the horizontal position
            $x++;
        }
        
        //    Unset the body / free the memory
        unset($body);
        
        //    Return image-object
        return $image;
    }
?>

AeroX @ aerox-studios (2008-05-11 02:54:04)

.bmp is just hex encoded RGB values.
All you need to do is open in binary mode and seperate the header from the body.
Decode the width and height from the header.
Then create the image pixel by pixel from the RGB values in the body.
function imagecreatefrombmp( $filename )
{
$file = fopen( $filename, "rb" );
$read = fread( $file, 10 );
while( !feof( $file ) && $read != "" )
{
$read .= fread( $file, 1024 );
}
$temp = unpack( "H*", $read );
$hex = $temp[1];
$header = substr( $hex, 0, 104 );
$body = str_split( substr( $hex, 108 ), 6 );
if( substr( $header, 0, 4 ) == "424d" )
{
$header = substr( $header, 4 );
// Remove some stuff?
$header = substr( $header, 32 );
// Get the width
$width = hexdec( substr( $header, 0, 2 ) );
// Remove some stuff?
$header = substr( $header, 8 );
// Get the height
$height = hexdec( substr( $header, 0, 2 ) );
unset( $header );
}
$x = 0;
$y = 1;
$image = imagecreatetruecolor( $width, $height );
foreach( $body as $rgb )
{
$r = hexdec( substr( $rgb, 4, 2 ) );
$g = hexdec( substr( $rgb, 2, 2 ) );
$b = hexdec( substr( $rgb, 0, 2 ) );
$color = imagecolorallocate( $image, $r, $g, $b );
imagesetpixel( $image, $x, $height-$y, $color );
$x++;
if( $x >= $width )
{
$x = 0;
$y++;
}
}
return $image;
}

clambert at whitecrown dot net (2001-06-16 13:47:56)

WBMP images are Wireless Bitmaps, not Windows Bitmaps. WBMP is used for bandwidth constrained, black and white, limited devices such as PDAs and Cell Phones.