Read bmp functions like GD

Read bmp functions like GD

Recently, we need to convert bmp images into jpg images, but what we can find on the internet is that bmp-to-gd classes or functions are more or less problematic. Most of the 16-bit bmp images are either completely black and completely powdered, or cannot be converted, while others do not support 32-bit bmp images at all. Finally, I found a solution on the php official website. The most widely circulated imagecreatefrombmp function on the Internet, similar to GD, is a problematic version and cannot correctly process 16-bit bmp images. However, some people have provided correction methods on the official website, the corrected code is as follows: /** * BMP creation function * @ Author simon * @ Modified * @ Param string $ filename path of bmp file * @ Example who use, who knows * @ Return resource of GD */ Function imagecreatefrombmp ($ filename ){ If (! $ F1 = fopen ($ filename, "rb ")) Return FALSE; $ FILE = unpack ("vfile_type/Vfile_size/Vreserved/Vbitmap_offset", fread ($ f1, 14 )); If ($ FILE ['File _ type']! = 19778) Return FALSE; $ BMP = unpack ('vheader _ size/Vwidth/Vheight/vplanes/vbits_per_pixel '. '/Vcompression/Vsize_bitmap/Vhoriz_resolution '. '/Vvert_resolution/Vcolors_used/Vcolors_important', fread ($ f1, 40 )); $ BMP ['Colors '] = pow (2, $ BMP ['bits _ per_pixel']); If ($ BMP ['size _ bitmap'] = 0) $ BMP ['size _ bitmap'] = $ FILE ['File _ size']-$ file ['bitmap _ offset']; $ BMP ['bytes _ per_pixel '] = $ BMP ['bits _ per_pixel']/8; $ BMP ['bytes _ per_pixel2 '] = ceil ($ BMP ['bytes _ per_pixel']); $ BMP ['desc'] = ($ BMP ['width'] * $ BMP ['bytes _ per_pixel ']/4 ); $ BMP ['desc']-= floor ($ BMP ['width'] * $ BMP ['bytes _ per_pixel ']/4 ); $ BMP ['demo'] = 4-(4 * $ BMP ['demo']); If ($ BMP ['desc'] = 4) $ BMP ['desc'] = 0; $ PALETTE = array (); If ($ BMP ['color'] <16777216 & $ BMP ['color']! = 65536) { $ PALETTE = unpack ('v'. $ BMP ['Colors '], fread ($ f1, $ BMP ['Colors'] * 4 )); } $ IMG = fread ($ f1, $ BMP ['size _ bitmap']); $ VIDE = chr (0 ); $ Res = imagecreatetruecolor ($ BMP ['width'], $ BMP ['height']); $ P = 0; $ Y = $ BMP ['height']-1; While ($ Y> = 0 ){ $ X = 0; While ($ X <$ BMP ['width']) { If ($ BMP ['bits _ per_pixel '] = 32 ){ $ COLOR = unpack ("V", substr ($ IMG, $ P, 3 )); $ B = ord (substr ($ IMG, $ P, 1 )); $ G = ord (substr ($ IMG, $ P + 1, 1 )); $ R = ord (substr ($ IMG, $ P + 2, 1 )); $ Color = imagecolorexact ($ res, $ R, $ G, $ B ); If ($ color =-1) $ Color = imagecolorallocate ($ res, $ R, $ G, $ B ); $ COLOR [0] = $ R * 256*256 + $ G * 256 + $ B; $ COLOR [1] = $ color; } Elseif ($ BMP ['bits _ per_pixel '] = 24 ){ $ COLOR = unpack ("V", substr ($ IMG, $ P, 3). $ VIDE ); } Elseif ($ BMP ['bits _ per_pixel '] = 16 ){ $ COLOR = unpack ("v", substr ($ IMG, $ P, 2 )); $ Blue = ($ COLOR [1] & 0x001f) <3) + 7; $ Green = ($ COLOR [1] & 0x03e0)> 2) + 7; $ Red = ($ COLOR [1] & 0xfc00)> 7) + 7; $ COLOR [1] = $ red * 65536 + $ green * 256 + $ blue; } Elseif ($ BMP ['bits _ per_pixel '] = 8 ){ $ COLOR = unpack ("n", $ VIDE. substr ($ IMG, $ P, 1 )); $ COLOR [1] = $ PALETTE [$ COLOR [1] + 1]; } Elseif ($ BMP ['bits _ per_pixel '] = 4 ){ $ COLOR = unpack ("n", $ VIDE. substr ($ IMG, floor ($ P), 1 )); If ($ P * 2) % 2 = 0) $ COLOR [1] = ($ COLOR [1]> 4 ); Else $ COLOR [1] = ($ COLOR [1] & 0x0F ); $ COLOR [1] = $ PALETTE [$ COLOR [1] + 1]; } Elseif ($ BMP ['bits _ per_pixel '] = 1 ){ $ COLOR = unpack ("n", $ VIDE. substr ($ IMG, floor ($ P), 1 )); If ($ P * 8) % 8 = 0) $ COLOR [1] = $ COLOR [1]> 7; Elseif ($ P * 8) % 8 = 1) $ COLOR [1] = ($ COLOR [1] & 0x40)> 6; Elseif ($ P * 8) % 8 = 2) $ COLOR [1] = ($ COLOR [1] & 0x20)> 5; Elseif ($ P * 8) % 8 = 3) $ COLOR [1] = ($ COLOR [1] & 0x10)> 4; Elseif ($ P * 8) % 8 = 4) $ COLOR [1] = ($ COLOR [1] & 0x8)> 3; Elseif ($ P * 8) % 8 = 5) $ COLOR [1] = ($ COLOR [1] & 0x4)> 2; Elseif ($ P * 8) % 8 = 6) $ COLOR [1] = ($ COLOR [1] & 0x2)> 1; Elseif ($ P * 8) % 8 = 7) $ COLOR [1] = ($ COLOR [1] & 0x1 ); $ COLOR [1] = $ PALETTE [$ COLOR [1] + 1]; } Else Return FALSE; Imagesetpixel ($ res, $ X, $ Y, $ COLOR [1]); $ X ++; $ P + = $ BMP ['bytes _ per_pixel ']; } $ Y --; $ P + = $ BMP ['demo']; } Fclose ($ f1 ); Return $ res; }