September 2017 Update

Task/Bitmap-Write-a-PPM-file/Zkl/bitmap-write-a-ppm-file.zkl

@@ -0,0 +1,17 @@
+// convert Windows BMP (bit map) image to PPM
+
+    // Read BMP file
+bmp:=File.stdin.read().howza(0); // BMP to memory (byte bucket), treat as bytes
+_assert_(bmp[0]==0x42,"Stdin not a BMP file");
+width:=bmp.toLittleEndian(18,2,False); height:=bmp.toLittleEndian(22,2,False); // signed
+println(width," x ",height);
+bmp.del(0,14 + bmp.toLittleEndian(14,2));  // get rid of header
+
+    // Write BMP to PPM image (in memory)
+ppm:=Data(width*height*3 + 100);  // sized byte bucket plus some header slop
+ppm.write("P6\n#rosettacode BMP to PPM test\n%d %d\n255\n".fmt(width,height));
+foreach y in ([height - 1 .. 0,-1]){  // BGR 1 byte each, image is stored upside down
+   bmp[y*width*3,width*3].pump(ppm,T(Void.Read,2),fcn(b,g,r){ return(r,g,b) });
+}
+
+File("foo.ppm","wb").write(ppm);  // File.stdout isn't binary, let GC close file