PHP处理bmp格式图片的步骤

Array
(
 [0] => 494
 [1] => 260
 [2] => 6
 [3] => width="494" height="260"
 [bits] => 24
 [mime] => image/x-ms-bmp
)

<?php
function ImageCreateFromBMP($filename) {
 //Ouverture du fichier en mode binaire
 if (!$f1 = fopen($filename, "rb"))
 return FALSE;
 //1 : Chargement des ent?tes FICHIER
 $FILE = unpack("vfile_type/Vfile_size/Vreserved/Vbitmap_offset", fread($f1, 14));
 if ($FILE['file_type'] != 19778)
 return FALSE;
 //2 : Chargement des ent?tes BMP
 $BMP = unpack('Vheader_size/Vwidth/Vheight/vplanes/vbits_per_pixel' .
 '/Vcompression/Vsize_bitmap/Vhoriz_resolution' .
 '/Vvert_resolution/Vcolors_used/Vcolors_important', fread($f1, 40));
 $BMP['colors'] = pow(2, $BMP['bits_per_pixel']);
 if ($BMP['size_bitmap'] == 0)
 $BMP['size_bitmap'] = $FILE['file_size'] - $FILE['bitmap_offset'];
 $BMP['bytes_per_pixel'] = $BMP['bits_per_pixel'] / 8;
 $BMP['bytes_per_pixel2'] = ceil($BMP['bytes_per_pixel']);
 $BMP['decal'] = ($BMP['width'] * $BMP['bytes_per_pixel'] / 4);
 $BMP['decal'] -= floor($BMP['width'] * $BMP['bytes_per_pixel'] / 4);
 $BMP['decal'] = 4 - (4 * $BMP['decal']);
 if ($BMP['decal'] == 4)
 $BMP['decal'] = 0;
 //3 : Chargement des couleurs de la palette
 $PALETTE = array();
 if ($BMP['colors'] < 16777216) {
 $PALETTE = unpack('V' . $BMP['colors'], fread($f1, $BMP['colors'] * 4));
 }
 //4 : Cr?ation de l'image
 $IMG = fread($f1, $BMP['size_bitmap']);
 $VIDE = chr(0);
 $res = imagecreatetruecolor($BMP['width'], $BMP['height']);
 $P = 0;
 $Y = $BMP['height'] - 1;
 while ($Y >= 0) {
 $X = 0;
 while ($X < $BMP['width']) {
 if ($BMP['bits_per_pixel'] == 24)
 $COLOR = unpack("V", substr($IMG, $P, 3) . $VIDE);
 elseif ($BMP['bits_per_pixel'] == 16) {
 $COLOR = unpack("n", substr($IMG, $P, 2));
 $COLOR[1] = $PALETTE[$COLOR[1] + 1];
 } elseif ($BMP['bits_per_pixel'] == 8) {
 $COLOR = unpack("n", $VIDE . substr($IMG, $P, 1));
 $COLOR[1] = $PALETTE[$COLOR[1] + 1];
 } elseif ($BMP['bits_per_pixel'] == 4) {
 $COLOR = unpack("n", $VIDE . substr($IMG, floor($P), 1));
 if (($P * 2) % 2 == 0)
 $COLOR[1] = ($COLOR[1] >> 4);
 else
 $COLOR[1] = ($COLOR[1] & 0x0F);
 $COLOR[1] = $PALETTE[$COLOR[1] + 1];
 }
 elseif ($BMP['bits_per_pixel'] == 1) {
 $COLOR = unpack("n", $VIDE . substr($IMG, floor($P), 1));
 if (($P * 8) % 8 == 0)
 $COLOR[1] = $COLOR[1] >> 7;
 elseif (($P * 8) % 8 == 1)
 $COLOR[1] = ($COLOR[1] & 0x40) >> 6;
 elseif (($P * 8) % 8 == 2)
 $COLOR[1] = ($COLOR[1] & 0x20) >> 5;
 elseif (($P * 8) % 8 == 3)
 $COLOR[1] = ($COLOR[1] & 0x10) >> 4;
 elseif (($P * 8) % 8 == 4)
 $COLOR[1] = ($COLOR[1] & 0x8) >> 3;
 elseif (($P * 8) % 8 == 5)
 $COLOR[1] = ($COLOR[1] & 0x4) >> 2;
 elseif (($P * 8) % 8 == 6)
 $COLOR[1] = ($COLOR[1] & 0x2) >> 1;
 elseif (($P * 8) % 8 == 7)
 $COLOR[1] = ($COLOR[1] & 0x1);
 $COLOR[1] = $PALETTE[$COLOR[1] + 1];
 } else
 return FALSE;
 imagesetpixel($res, $X, $Y, $COLOR[1]);
 $X++;
 $P += $BMP['bytes_per_pixel'];
 }
 $Y--;
 $P+=$BMP['decal'];
 }
 //Fermeture du fichier
 fclose($f1);
 return $res;
}
$pic = '2.bmp';
$res = ImageCreateFromBMP($pic);
imagepng($res, '1.png');
imagejpeg($res, '1.jpeg');