%?A?film?grain?removal?example?by?iterative?steering?kernel?regression
%
%?written?by?hiro?June?17?2007

%?load?image
img?=?double（imread（‘JFKreg.jpg‘））;
[NM]?=?size（img（::1））;

%?convert?the?image?into?the?YCrCb?channels
[Y?Cr?Cb]?=?RGB2YCC（img）;

%?the?input?image
y?=?zeros（N?M?3）;
y（::1）?=?Y;
y（::2）?=?Cr;
y（::3）?=?Cb;

%?pilot?estimation?by?second?order?classic?kernel?regression
%?on?the?luminance?channel
h?=?0.5;????%?the?global?smoothing?parameter
r?=?1;??????%?the?upscaling?factor
ksize?=?5;??%?the?kernel?size
[zc?zx1c?zx2c]?=?ckr2_regular（y（::1）?h?r?ksize）;

%?iteartive?steering?kernel?regression?（second?order）
IT?=?5;?????%?the?total?number?of?iterations
wsize?=?11;??%?the?size?of?the?local?orientation?analysis?window
lambda?=?1;??%?the?regularization?for?the?elongation?parameter
alpha?=?0.5;?%?the?structure?sensitive?parameter
h?=?2.3;?????%?the?global?smoothing?parameter
ksize?=?11;??%?the?kernel?size
z?=?zeros（N?M?3?IT+1）;
zx1?=?zeros（N?M?3?IT+1）;
zx2?=?zeros（N?M?3?IT+1）;
z（:::1）?=?y;
zx1（::1）?=?zx1c;
zx2（::1）?=?zx2c;

for?i?=?2?:?IT+1
????%?compute?steering?matrix?from?the?Y?channel
????C?=?steering（zx1（::i-1）?zx2（::i-1）?ones（size（img））?wsize?lambda?alpha）;
????%?steering?kernel?regression
????%?Y?channel
????[zs?zx1s?zx2s]?=?skr2_regular（z（::1i-1）?h?C?r?ksize）;
????z（::1i）?=?zs;
????zx1（::i）?=?zx1s;
????zx2（::i）?=?zx2s;
????%?Cr?channel
????[zs?zx1s?zx2s]?=?skr2_regular（z（::2i-1）?h?C?r?ksize）;
????z（::2i）?=?zs;
????%?Cb?channel
????[zs?zx1s?zx2s]?=?skr2_regular（z（::3i-1）?h?C?r?ksize）;
????z（::3i）?=?zs;
end

%?display?images
zRGB?=?YCC2RGB（z（::14）?z（::24）?z（::34））;
figure;?imagesc（uint8（img））;?colormap（gray）;?axis?image;
title（‘The?original?image‘）;
figure;?imagesc（uint8（zRGB））;?colormap（gray）;?axis?image;
title（‘The?denoised?image?by?iterative?steering?kernel?regression?3?iterations‘）;
gray_reverse?=?gray;
gray_reverse?=?gray_reverse（64:-1:1?:）;
figure;?imagesc（abs（z（::11）?-?z（::14）））;?colormap（gray_reverse）;?axis?image;?colorbar;
title（‘The?absolute?residual?image?in?the?luminance?channel‘）;