仿GD读取bmp函数

最近在工作中需要把bmp图片转成jpg图片，但无奈的是网上能找到的bmp转gd的类或函数或多或少都有些问题。其中绝大多数在处理16位bmp图片时要么全黑全粉，要么干脆转换不出，其余有些根本不支持32位的bmp图片。 最后我终于在php的官网上找到了解决方法。原来网上流传最广的一个仿GD的imagecreatefrombmp函数是一个有问题的版本，无法正确处理16位bmp图片，但好在官网上有人给出了修正方法，修正好的代码如下： /** * BMP 创建函数 * @author simon * @modified by 天心流水 * @param string $filename path of bmp file * @example who use,who knows * @return resource of GD */ function imagecreatefrombmp( $filename ) {if ( !$f1 = fopen( $filename, "rb" ) )return FALSE;$FILE = unpack( "vfile_type/Vfile_size/Vreserved/Vbitmap_offset", fread( $f1, 14 ) );if ( $FILE['file_type'] != 19778 )return FALSE;$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;$PALETTE = array(); if ($BMP['colors'] { $PALETTE = unpack('V'.$BMP['colors'], fread($f1,$BMP['colors']*4)); }$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 if ( $BMP['bits_per_pixel'] == 32 ){$COLOR = unpack( "V", substr( $IMG, $P, 3 ) );$B = ord(substr($IMG, $P,1));$G = ord(substr($IMG, $P+1,1));$R = ord(substr($IMG, $P+2,1));$color = imagecolorexact( $res, $R, $G, $B );if ( $color == -1 )$color = imagecolorallocate( $res, $R, $G, $B );$COLOR[0] = $R*256*256+$G*256+$B;$COLOR[1] = $color;} elseif ( $BMP['bits_per_pixel'] == 24 ) {$COLOR = unpack( "V", substr( $IMG, $P, 3 ) . $VIDE ); } elseif ( $BMP['bits_per_pixel'] == 16 ){ $COLOR = unpack("v",substr($IMG,$P,2)); $blue = (($COLOR[1] & 0x001f) $green = (($COLOR[1] & 0x03e0) >> 2) + 7; $red = (($COLOR[1] & 0xfc00) >> 7) + 7; $COLOR[1] = $red * 65536 + $green * 256 + $blue;} 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];}elsereturn FALSE;imagesetpixel( $res, $X, $Y, $COLOR[1] );$X++;$P += $BMP['bytes_per_pixel'];}$Y--;$P += $BMP['decal'];}fclose( $f1 );return $res;}复制代码