[GD] Create a BMP format picture (imagebmp) _php Tutorial

GD library does not produce BMP image function, so wrote a, this function has a compression algorithm is not written, but already enough. The students who need it can take a look.

int Imagebmp (resource image [, string filename [, int $bit [, int compression]])

$im: Image Resources
$filename: If you want to save as a file, specify a filename, or empty it directly in the browser output
$bit: Image quality (1, 4, 8, 16, 24, 32 bit)
$compression: compression, 0 uncompressed, 1 compressed using RLE8 compression algorithm

Note: This function still requires the support of the GD library.

Demo:

$im = Imagecreatefrompng ("Test.png");
Imagebmp ($im);
Imagedestroy ($im);
Source:

/**
* Create BMP format Picture
*
* @author: Legend (legendsky@hotmail.com)
* @link: http://www.ugia.cn/?p=96
* @description: Create bitmap-file with GD Library
* @version: 0.1
*
* @param resource $im image Resources
* @param string $filename If you want to save as a file, specify a filename, or empty it directly in the browser output
* @param integer $bit image quality (1, 4, 8, 16, 24, 32 bit)
* @param integer $compression compression, 0 uncompressed, 1 compressed using RLE8 compression algorithm
*
* @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 = = +)//todo:32 bit
{
$bit = 24;
}

$bits = POW (2, $bit);

Adjust Palette
Imagetruecolortopalette ($im, True, $bits);
$width = Imagesx ($im);
$height = Imagesy ($im);
$colors _num = Imagecolorstotal ($im);

if ($bit <= 8)
{
Color Index
$rgb _quad =;
for ($i = 0; $i < $colors _num; $i + +)
{
$colors = Imagecolorsforindex ($im, $i);
$rgb _quad. = Chr ($colors [Blue]). Chr ($colors [green]). Chr ($colors [red]). "";
}

Bitmap data
$bmp _data =;

Non-compressed
if ($compression = = 0 | | $bit < 8)
{
if (!in_array ($bit, Array (1, 4, 8)))
{
$bit = 8;
}

$compression = 0;

The number of bytes per line must be a multiple of 4, padded.
$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. = $extra;
}
}
RLE8 compression
else if ($compression = = = 1 && $bit = = 8)
{
for ($j = $height-1; $j >= 0; $j-)
{
$last _index = "";
$same _num = 0;
for ($i = 0; $i <= $width; $i + +)
{
$index = Imagecolorat ($im, $i, $j);
if ($index!== $last _index | | $same _num > 255)
&nb

http://www.bkjia.com/PHPjc/508374.html www.bkjia.com true http://www.bkjia.com/PHPjc/508374.html techarticle GD Library does not produce BMP image function, so wrote a, this function has a compression algorithm is not written, but already enough. The students who need it can take a look. int image ...

