[GD] generating bmp images (imagebmp)

[GD] generates an image in bmp format (imagebmp). read [GD] generates an image in bmp format (imagebmp). the GD library does not generate a function for bmp images, so I wrote one myself, there is still a compression algorithm for this function, but it is enough. For more information, see. Intimagebmp (resourceimage [, stringfilename

There is no bmp image generation function in the GD library, so I wrote one myself. there is still a compression algorithm not written, but it is enough. For more information, see.

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

$ Im: Image resources
$ Filename: If you want to save it as a file, specify the file name. if it is null, it is output directly in the browser.
$ Bit: image quality (1, 4, 8, 16, 24, 32 bits)
$ Compression: compression method. 0 indicates no compression, and 1 uses RLE8 compression algorithm for compression.

Note: This function still needs the support of the GD Library.

Demo:

$ Im = imagecreatefrompng ("test.png ");
Imagebmp ($ im );
Imagedestroy ($ im );
Source:

/**
* Create a bmp image
*
* @ 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 resource
* @ Param string $ filename if you want to save it as a file, specify the file name. if it is null, the file is output directly in the browser.
* @ Param integer $ bit image quality (1, 4, 8, 16, 24, 32 bits)
* @ Param integer $ compression: compression mode. 0 indicates no compression, and 1 indicates 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 = 32) // todo: 32 bit
{
$ Bit = 24;
}

$ Bits = pow (2, $ bit );

// Adjust the color 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']). "\ 0 ";
}

// 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 in each row must be a multiple of 4.
$ 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 compression
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
{
// The number of bytes in each row must be a multiple of 4.
$ Extra = '';
$ Padding = 4-($ width * ($ bit/8) % 4;
If ($ padding % 4! = 0)
{
$ Extra = str_repeat ("\ 0", $ padding );
}

// Bitmap data
$ 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;
}

// Bitmap file header
$ File_header = "BM". pack ("V3", 54 + $ size_quad + $ size_data, 0, 54 + $ size_quad );

// Bitmap Header
$ Info_header = pack ("V3v2V *", 0x28, $ width, $ height, 1, $ bit, $ compression, $ size_data, 0, 0, $ colors_num, 0 );

// Write a file
If ($ filename! = '')
{
$ Fp = fopen ("test.bmp", "wb ");

Fwrite ($ fp, $ file_header );
Fwrite ($ fp, $ info_header );
Fwrite ($ fp, $ rgb_quad );
Fwrite ($ fp, $ BMP _data );
Fclose ($ fp );

Return 1;
}

// Browser output
Header ("Content-Type: image/bmp ");
Echo $ file_header. $ info_header;
Echo $ rgb_quad;
Echo $ BMP _data;

Return 1;
}
Reference: BMP file format analysis (the source is not found ...)

Original article. For more information, see the source.

Http://www.ugia.cn /? P = 96