Alpha channel remover from old BPG pictures
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#!/usr/bin/perl | |
# Removes alpha channel from BPG v0.9.3- image, so it can be decoded with libbpg v0.9.4+. | |
# Implemented by Vitaly "_Vi" Shukela in 2015 | |
# License: MIT | |
read STDIN,$_,4; | |
my $magic=unpack("N", $_); | |
printf STDERR "magic: %08X\n", $magic; | |
print STDOUT pack("N", $magic); | |
read STDIN,$_,1; | |
my $q = unpack("C",$_); | |
my $pf = $q >> 5; | |
my $al = ($q >> 4) & 1; | |
my $bd = $q & 0xF; | |
printf STDERR "PixelFormat: %d alpha: %d bitdepth: %d\n", $pf, $al, $bd+8; | |
my $q_ = ($pf << 5) | $bd; | |
print STDOUT pack("C", $q_); | |
read STDIN,$_,1; | |
my $q2 = unpack("C",$_); | |
my $cs = $q2 >> 4; | |
my $extp = ($q2 & 0x08); | |
my $alpha2 = ($q2 & 0x04); | |
my $lrf = ($q2 & 0x02); | |
my $reserz = ($q2 & 0x01); | |
printf STDERR "ColorSpace: %d ExtPresent: %d Alpha2: %d LimitedRange: %d ReservedZero: %d\n", $cs, $extp, $alpha2, $lrf, $reserz; | |
my $q2_ = ($cs << 4) | $extp | $lrf | $reserz; | |
print STDOUT pack("C", $q2_); | |
sub read_ue7($) { | |
my $maxbytes = shift; | |
my $x = 0; | |
for(my $i=0;$i<$maxbytes;++$i) { | |
read STDIN,$_,1; | |
my $q = unpack("C",$_); | |
$x *= 128; | |
if ($q & 0x80) { | |
$x += $q & 0x7F; | |
} else { | |
$x += $q; | |
return $x; | |
} | |
} | |
return $x; | |
} | |
sub write_ue7($) { | |
my $x = shift; | |
my $last = 0x00; | |
my $s = ""; | |
while ($x > 127) { | |
$s = pack("C", ($x & 0x7F) | $last) . $s; | |
$x = $x >> 7; | |
$last = 0x80; | |
} | |
$s = pack("C", ($x & 0x7F) | $last) . $s; | |
print STDOUT $s; | |
} | |
my ($w, $h) = (read_ue7(4), read_ue7(4)); | |
printf STDERR "Width: %d Height: %d\n", $w, $h; | |
write_ue7($w); write_ue7($h); | |
my $pdl = read_ue7(4); | |
printf STDERR "Picture data length: %d\n", $pdl; | |
write_ue7($pdl); | |
my $edl; | |
if ($extp) { | |
$edl = read_ue7(4); | |
printf STDERR "Extension data length: %d\n", $edl; | |
write_ue7($edl); | |
} | |
my $adl; | |
if ($al or $alpha2) { | |
$adl = read_ue7(4); | |
printf STDERR "Alpha data length: %d\n", $adl; | |
} | |
if ($extp) { | |
read STDIN, $_, $edl; | |
print STDOUT $_; | |
} | |
read STDIN, $_, $pdl; | |
print STDOUT $_; | |
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