Add a method to get pixel data and add a test for it to scripts/tryme.pl

lib/MAS/TIFF/IFD.pm

@@ -187,6 +187,60 @@ sub strip {
   return $bytes;
 }
 
+#
+# With the strip, each row is stored in a contiguous byte sequence, with possibly some
+# unused bits at the end.
+#
+# Returns zero for black, one for white.
+#
+
+sub pixel_at {
+  use integer;
+
+  my $self = shift;
+  my ($x, $y) = @_;
+
+  if ($self->samples_per_pixel != 1) {
+    die "Sorry, only images with one sample per pixel are supported!";
+  }
+
+  if ($self->bits_per_sample != 1) {
+    die "Sorry, only images with one bit per sample are supported!";
+  }
+
+  if (($x < 0) || ($x >= $self->image_width)) {
+    die "x must be in range 0.." . ($self->image_width - 1) . "!";
+  }
+
+  if (($y < 0) || ($y >= $self->image_length)) {
+    die "y must be in range 0.." . ($self->image_width - 1) . "!";
+  }
+
+  my $index = $y / $self->rows_per_strip;
+  my $strip = $self->strip($index);
+
+  my $row = $y % $self->rows_per_strip;
+
+  my $bytes_per_row = $self->image_width / 8 + (($self->image_width % 8) != 0 ? 1 : 0);
+  my $byte_index = ($row * $bytes_per_row) + ($x / 8);
+  my $byte = ord substr($strip, $byte_index, 1);
+  my $bit_index = 7 - ($x % 8);
+  my $bit = ($byte >> $bit_index) & 0x01;
+  my $row_offset =
+
+  my $pi = $self->photometric_interpretation;
+
+  if ($pi eq 'MinIsWhite') {
+    return !$bit;
+  }
+  elsif ($pi eq 'MinIsBlack') {
+    return $bit;
+  }
+  else {
+    die "Sorry, only MinIsWhite and MinIsBlack are supported photometric interpretations!";
+  }
+}
+
 sub is_image {
   my $self = shift;
 

scripts/tryme.pl

@@ -15,21 +15,23 @@
 use MAS::TIFF::IFD;
 use MAS::TIFF::File;
 
-sub read_tif {
-  my $path = shift;
-
-  my $tif = MAS::TIFF::File->new($path);
-  $tif->dump;
-
-  $tif->close;
-}
-
-
 my $path = 't/original.tif';
 #my $path = 't/noisy.tif';
 #my $path = 't/diffuse.tif';
 #my $path = 't/multi.tif';
-read_tif($path);
 
+my $tif = MAS::TIFF::File->new($path);
+$tif->dump;
+
+for my $ifd ($tif->ifds) {
+  for my $y (0..70) {
+    for my $x (0..70) {
+      print $ifd->pixel_at($x, $y) ? '.' : '*';
+    }
+    print "\n";
+  }
+}
+
+$tif->close;
 
 exit 0;