Data commit

Task/Bitmap-Read-a-PPM-file/Raku/bitmap-read-a-ppm-file.raku

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+class Pixel { has UInt ($.R, $.G, $.B) }
+class Bitmap {
+    has UInt ($.width, $.height);
+    has Pixel @.data;
+}
+
+role PGM {
+    has @.GS;
+    method P5 returns Blob {
+	"P5\n{self.width} {self.height}\n255\n".encode('ascii')
+	~ Blob.new: self.GS
+    }
+}
+
+sub load-ppm ( $ppm ) {
+    my $fh    = $ppm.IO.open( :enc('ISO-8859-1') );
+    my $type  = $fh.get;
+    my ($width, $height) = $fh.get.split: ' ';
+    my $depth = $fh.get;
+    Bitmap.new( width => $width.Int, height => $height.Int,
+      data => ( $fh.slurp.ords.rotor(3).map:
+        { Pixel.new(R => $_[0], G => $_[1], B => $_[2]) } )
+    )
+}
+
+sub grayscale ( Bitmap $bmp ) {
+    $bmp.GS = map { (.R*0.2126 + .G*0.7152 + .B*0.0722).round(1) min 255 }, $bmp.data;
+}
+
+my $filename = './camelia.ppm';
+
+my Bitmap $b = load-ppm( $filename ) but PGM;
+
+grayscale($b);
+
+'./camelia-gs.pgm'.IO.open(:bin, :w).write: $b.P5;