PHP uses the GD library to generate images in bmp format (imagebmp)

/**
* Create bmp format pictures
*
* @author: legend
* @description: create Bitmap-File with GD library
* @version: 0.1
*
* @param resource $im image resource
* @param string $filename If you want to save as a file, please specify the file name. If it is empty, it will be output directly in the browser
* @param integer $bit image quality (1, 4, 8, 16, 24, 32 bits)
* @param integer $compression compression Mode, 0 means no compression, 1 uses RLE8 compression algorithm for compression
*
* @return integer
*/
function imagebmp(&$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']) . “