"Ken" <ha************@yahoo.com> wrote in message
news:ea**************************@posting.google.c om...
I need to convert 32 bit Windows bitmaps to jpgs with PHP.
I used the function from http://groups.google.com/groups?
hl=en&lr=&ie=UTF-8&oe=UTF-8&safe=off&selm=a164f4b5.0311302128.40fb37f4%
40posting.google.com to convert bitmaps to jpgs.
It works very well for my 24 bit bitmaps, but I cannot figure out how
to
get it to work with 32 bits. I tried adding an additional scan line
and
the image appears in the correct size, but the colors are way off and
some of the data is missing. I also tried putting $a in different
places within the $gd_scan_line string:
This did not work:
$b = $scan_line{$j++};
$g = $scan_line{$j++};
$r = $scan_line{$j++};
$a = $scan_line{$j++};
$gd_scan_line .= "\x$a$r$g$b";
Can anyone help?
Ken
You were close. Should have been $gd_scan_line .= "$a$r$g$b". Actually, the
GD library interprets the alpha value as transparency (255 = fully
transparent) while Windows sees it as opacity (0 = fully transparent). So we
actually need to substract $a from 255 to get the correct value.
Here's the update code. Improved it a bit by avoiding the use of a temporary
file.
<?
function ConvertBMP2GD($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 - ($scan_line_size & 0x03)
: 0;
for($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, $scan_line_size);
if($bits == 24) {
$gd_scan_line = "";
$j = 0;
while($j < $scan_line_size) {
$b = $scan_line{$j++};
$g = $scan_line{$j++};
$r = $scan_line{$j++};
$gd_scan_line .= "\xFF$r$g$b";
}
}
else if($bits == 32) {
$gd_scan_line = "";
$j = 0;
while($j < $scan_line_size) {
$b = $scan_line{$j++};
$g = $scan_line{$j++};
$r = $scan_line{$j++};
$a = chr(255 - ord($scan_line{$j++}));
$gd_scan_line .= "$a$r$g$b";
}
}
else if($bits == 8) {
$gd_scan_line = $scan_line;
}
else if($bits == 4) {
$gd_scan_line = "";
$j = 0;
while($j < $scan_line_size) {
$byte = ord($scan_line{$j++});
$p1 = chr($byte >> 4);
$p2 = chr($byte & 0x0F);
$gd_scan_line .= "$p1$p2";
} $gd_scan_line = substr($gd_scan_line, 0, $width);
}
else if($bits == 1) {
$gd_scan_line = "";
$j = 0;
while($j < $scan_line_size) {
$byte = ord($scan_line{$j++});
$p1 = chr((int) (($byte & 0x80) != 0));
$p2 = chr((int) (($byte & 0x40) != 0));
$p3 = chr((int) (($byte & 0x20) != 0));
$p4 = chr((int) (($byte & 0x10) != 0));
$p5 = chr((int) (($byte & 0x08) != 0));
$p6 = chr((int) (($byte & 0x04) != 0));
$p7 = chr((int) (($byte & 0x02) != 0));
$p8 = chr((int) (($byte & 0x01) != 0));
$gd_scan_line .= "$p1$p2$p3$p4$p5$p6$p7$p8";
} $gd_scan_line = substr($gd_scan_line, 0, $width);
}
fwrite($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;
}
$img = imagecreatefrombmp("test32bit.bmp");
imagealphablending($img, false);
imagesavealpha($img, true);
imagepng($img, "test.png");
?>
<img src="test.png">
