PHP仿GD生成BMP图片
- 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, $bit);
-
- // 调整调色板
- imagetruecolortopalette($im, true, $bits);
- $width = imagesx($im);
- $height = imagesy($im);
- $colors_num = imagecolorstotal($im);
-
- if ($bit <= 8)
- {
- // 颜色索引
- $rgb_quad = '';
- for ($i = 0; $i < $colors_num; $i ++)
- {
- $colors = imagecolorsforindex($im, $i);
- $rgb_quad .= chr($colors['blue']) . chr($colors['green']) . chr($colors['red']) . " ";
- }
- // 位图数据
- $bmp_data = '';
- // 非压缩
- if ($compression == 0 || $bit < 8)
- {
- if (!in_array($bit, array(1, 4, 8)))
- {
- $bit = 8;
- }
- $compression = 0;
-
- // 每行字节数必须为4的倍数，补齐。
- $extra = '';
- $padding = 4 - ceil($width / (8 / $bit)) % 4;
- if ($padding % 4 != 0)
- {
- $extra = str_repeat(" ", $padding);
- }
- for ($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 .= $extra;
- }
- }
- // RLE8 压缩
- else if ($compression == 1 && $bit == 8)
- {
- for ($j = $height - 1; $j >= 0; $j --)
- {
- $last_index = "
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