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php生成bmp圖像,PHP仿GD生成BMP圖檔

function imagebmp(&$im, $filename = '', $bit = 8, $compression = 0)

{

if (!in_array($bit, array(1, 4, 8, 16, 24, 32)))

{

$bit = 8;

}

else if ($bit == 32) // todo:32 bit

{

$bit = 24;

}

$bits = pow(2, $bit);

// 調整調色闆

imagetruecolortopalette($im, true, $bits);

$width = imagesx($im);

$height = imagesy($im);

$colors_num = imagecolorstotal($im);

if ($bit <= 8)

{

// 顔色索引

$rgb_quad = '';

for ($i = 0; $i < $colors_num; $i ++)

{

$colors = imagecolorsforindex($im, $i);

$rgb_quad .= chr($colors['blue']) . chr($colors['green']) . chr($colors['red']) . "\0";

}

// 位圖資料

$bmp_data = '';

// 非壓縮

if ($compression == 0 || $bit < 8)

{

if (!in_array($bit, array(1, 4, 8)))

{

$bit = 8;

}

$compression = 0;

// 每行位元組數必須為4的倍數,補齊。

$extra = '';

$padding = 4 - ceil($width / (8 / $bit)) % 4;

if ($padding % 4 != 0)

{

$extra = str_repeat("\0", $padding);

}

for ($j = $height - 1; $j >= 0; $j --)

{

$i = 0;

while ($i < $width)

{

$bin = 0;

$limit = $width - $i < 8 / $bit ? (8 / $bit - $width + $i) * $bit : 0;

for ($k = 8 - $bit; $k >= $limit; $k -= $bit)

{

$index = imagecolorat($im, $i, $j);

$bin |= $index << $k;

$i ++;

}

$bmp_data .= chr($bin);

}

$bmp_data .= $extra;

}

}

// RLE8 壓縮

else if ($compression == 1 && $bit == 8)

{

for ($j = $height - 1; $j >= 0; $j --)

{

$last_index = "\0";

$same_num = 0;

for ($i = 0; $i <= $width; $i ++)

{

$index = imagecolorat($im, $i, $j);

if ($index !== $last_index || $same_num > 255)

{

if ($same_num != 0)

{

$bmp_data .= chr($same_num) . chr($last_index);

}

$last_index = $index;

$same_num = 1;

}

else

{

$same_num ++;

}

}

$bmp_data .= "\0\0";

}

$bmp_data .= "\0\1";

}

$size_quad = strlen($rgb_quad);

$size_data = strlen($bmp_data);

}

else

{

// 每行位元組數必須為4的倍數,補齊。

$extra = '';

$padding = 4 - ($width * ($bit / 8)) % 4;

if ($padding % 4 != 0)

{

$extra = str_repeat("\0", $padding);

}

// 位圖資料

$bmp_data = '';

for ($j = $height - 1; $j >= 0; $j --)

{

for ($i = 0; $i < $width; $i ++)

{

$index = imagecolorat($im, $i, $j);

$colors = imagecolorsforindex($im, $index);

if ($bit == 16)

{

$bin = 0 << $bit;

$bin |= ($colors['red'] >> 3) << 10;

$bin |= ($colors['green'] >> 3) << 5;

$bin |= $colors['blue'] >> 3;

$bmp_data .= pack("v", $bin);

}

else

{

$bmp_data .= pack("c*", $colors['blue'], $colors['green'], $colors['red']);

}

// todo: 32bit;

}

$bmp_data .= $extra;

}

$size_quad = 0;

$size_data = strlen($bmp_data);

$colors_num = 0;

}

// 位圖檔案頭

$file_header = "BM" . pack("V3", 54 + $size_quad + $size_data, 0, 54 + $size_quad);

// 位圖資訊頭

$info_header = pack("V3v2V*", 0x28, $width, $height, 1, $bit, $compression, $size_data, 0, 0, $colors_num, 0);

// 寫入檔案

if ($filename != '')

{

$fp = fopen($filename, "wb");

fwrite($fp, $file_header);

fwrite($fp, $info_header);

fwrite($fp, $rgb_quad);

fwrite($fp, $bmp_data);

fclose($fp);

return true;

}

// 浏覽器輸出

header("Content-Type: image/bmp");

echo $file_header . $info_header;

echo $rgb_quad;

echo $bmp_data;

return true;

}