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Optimized version of imagecreatefrombmp()

P: n/a
Unrolled the scanline conversion loop into a lamda function. Should be
slightly quicker.

<?

function ConvertBMP2GD($src, $dest = false) {
if(!($src_f = fopen($src, "rb"))) {
trigger_error("Can't open $src", E_WARNING);
return false;
}
if(!($dest_f = fopen($dest, "wb"))) {
trigger_error("Can't open $dest", E_WARNING);
return false;
}
$header = unpack("vtype/Vsize/v2reserved/Voffset", fread($src_f, 14));
$info =
unpack("Vsize/Vwidth/Vheight/vplanes/vbits/Vcompression/Vimagesize/Vxres/Vyr
es/Vncolor/Vimportant", fread($src_f, 40));

extract($info);
extract($header);

if($type != 0x4D42) { // signature "BM"
return false;
}

$palette_size = $offset - 54;
$ncolor = $palette_size / 4;
$gd_header = "";
// true-color vs. palette
$gd_header .= ($palette_size == 0) ? "\xFF\xFE" : "\xFF\xFF";
$gd_header .= pack("n2", $width, $height);
$gd_header .= ($palette_size == 0) ? "\x01" : "\x00";
if($palette_size) {
$gd_header .= pack("n", $ncolor);
}
// no transparency
$gd_header .= "\xFF\xFF\xFF\xFF";

fwrite($dest_f, $gd_header);

if($palette_size) {
$palette = fread($src_f, $palette_size);
$gd_palette = "";
$j = 0;
while($j < $palette_size) {
$b = $palette{$j++};
$g = $palette{$j++};
$r = $palette{$j++};
$a = $palette{$j++};
$gd_palette .= "$r$g$b$a";
}
$gd_palette .= str_repeat("\x00\x00\x00\x00", 256 - $ncolor);
fwrite($dest_f, $gd_palette);
}

$scan_line_size = (($bits * $width) + 7) >> 3;
$scan_line_align = ($scan_line_size & 0x03) ? 4 - ($scan_line_size & 0x03)
: 0;
if($bits == 24) {
$j = 0;
$k = 1;
$m = 2;
$function = 'return "';
while($j < $scan_line_size) {
$function .= "\\0\{\$s\{$m}}\{\$s\{$k}}\{\$s\{$j}}";
$j += 3;
$k += 3;
$m += 3;
}
$function .= '";';
}
else if($bits == 32) {
$function = 'return "';
$j = 0;
$k = 1;
$m = 2;
$n = 3;
while($j < $scan_line_size) {
$function .= "\\0\{\$s\{$m}}\{\$s\{$k}}\{\$s\{$j}}";
$j += 4;
$k += 4;
$m += 4;
$n += 4;
}
$function .= '";';
}
else if($bits == 8) {
$function = 'return $s;';
}
else if($bits == 4) {
$j = 0;
$function = '';
while($j < $scan_line_size) {
$function .= "\$b=ord(\$s\{$j});";
$function .= "\$a[]=chr(\$b>>4);";
$function .= "\$a[]=chr(\$b&0x0F);";
$j++;
}
$function .= "return substr(implode(\$a), 0, \$width);";
}
else if($bits == 1) {
$j = 0;
$function = '';
while($j < $scan_line_size) {
$function .= "\$b=ord(\$s\{$j});";
$function .= "\$a[]=chr((int)((\$b&0x80)!=0));";
$function .= "\$a[]=chr((int)((\$b&0x40)!=0));";
$function .= "\$a[]=chr((int)((\$b&0x20)!=0));";
$function .= "\$a[]=chr((int)((\$b&0x10)!=0));";
$function .= "\$a[]=chr((int)((\$b&0x08)!=0));";
$function .= "\$a[]=chr((int)((\$b&0x04)!=0));";
$function .= "\$a[]=chr((int)((\$b&0x02)!=0));";
$function .= "\$a[]=chr((int)((\$b&0x01)!=0));\n";
$j++;
}
$function .= "return substr(implode(\$a), 0, \$width);";
}

$f = create_function('$s, $width', $function);

for($i = 0, $l = $height - 1; $i < $height; $i++, $l--) {
// BMP stores scan lines starting from bottom
fseek($src_f, $offset + (($scan_line_size + $scan_line_align) * $l));
$scan_line = fread($src_f, $scan_line_size);
$gd_scan_line = $f($scan_line, $width);

fwrite($dest_f, $gd_scan_line);
}
fclose($src_f);
fclose($dest_f);
return true;
}
class MemoryStream {
var $position;
var $varname;
var $buffer;

function stream_open($path, $mode, $options, &$opened_path)
{
$url = parse_url($path);
$this->varname = $url["host"];
$this->position = 0;
$this->buffer = @$GLOBALS[$this->varname];

return true;
}

function stream_close()
{
$GLOBALS[$this->varname] = $this->buffer;
}

function stream_read($count)
{
$ret = substr($this->buffer, $this->position, $count);
$this->position += strlen($ret);
return $ret;
}

function stream_write($data)
{
$this->buffer .= $data;
$this->position += strlen($data);
return strlen($data);
}

function stream_tell()
{
return $this->position;
}

function stream_eof()
{
return $this->position >= strlen($this->buffer);
}

function stream_stat() {
return array( 'size' => strlen($this->buffer) );
}
}

function imagecreatefrombmp($filename) {
// use a memory stream instead of a temp file
// where possible
if(function_exists('stream_wrapper_register')
&& stream_wrapper_register("mem", "MemoryStream")) {
$tmp_name = "mem://GD_TMP_FILE";
$del_tmp = false;
}
else {
$tmp_name = tempnam("/tmp", "GD");
$del_tmp = true;
}
if(ConvertBMP2GD($filename, $tmp_name)) {
$img = imagecreatefromgd($tmp_name);
if($del_tmp) {
unlink($tmp_name);
}
return $img;
} return false;
}

$img = imagecreatefrombmp("test24bit.bmp");
imagepng($img, "test.png");

?>
<img src="test.png">
Jul 17 '05 #1
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1 Reply


P: n/a
What about 16bit-Bitmaps?
They don't seem to work..
Do you have any idea?

Michael

Jul 17 '05 #2

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