| 1 | use super::Pixel; |
| 2 | |
| 3 | struct VQBox<'a> { |
| 4 | pixels: &'a mut [Pixel], |
| 5 | max: Pixel, |
| 6 | min: Pixel, |
| 7 | } |
| 8 | |
| 9 | fn avg_u8(a: u8, b: u8) -> u8 { |
| 10 | (a & b) + ((a ^ b) >> 1) |
| 11 | } |
| 12 | |
| 13 | impl<'a> VQBox<'a> { |
| 14 | fn new(pixels: &'a mut [Pixel]) -> Self { |
| 15 | let mut max = Pixel{ r: 0, g: 0, b: 0 }; |
| 16 | let mut min = Pixel{ r: 255, g: 255, b: 255 }; |
| 17 | for pix in pixels.iter() { |
| 18 | max = max.max(*pix); |
| 19 | min = min.min(*pix); |
| 20 | } |
| 21 | Self { pixels, max, min } |
| 22 | } |
| 23 | fn can_split(&self) -> bool { |
| 24 | let dr = self.max.r - self.min.r; |
| 25 | let dg = self.max.g - self.min.g; |
| 26 | let db = self.max.b - self.min.b; |
| 27 | (dr | dg | db) != 0 |
| 28 | } |
| 29 | fn sort<F>(arr: &mut [Pixel], idx: F) -> usize where F: Fn(&Pixel) -> usize { |
| 30 | let mut buckets: Vec<Vec<Pixel>> = Vec::with_capacity(256); |
| 31 | let mut counts = [0; 256]; |
| 32 | for pix in arr.iter() { |
| 33 | counts[idx(pix)] += 1; |
| 34 | } |
| 35 | for i in 0..256 { |
| 36 | buckets.push(Vec::with_capacity(counts[i])); |
| 37 | } |
| 38 | for pix in arr.iter() { |
| 39 | buckets[idx(pix)].push(*pix); |
| 40 | } |
| 41 | let mut start = 0; |
| 42 | let mut pivot = 0; |
| 43 | let mut cand1 = 0; |
| 44 | for bucket in buckets.iter() { |
| 45 | let end = bucket.len(); |
| 46 | if (start > 0) && (start <= arr.len() / 2) { |
| 47 | pivot = start + end; |
| 48 | cand1 = start; |
| 49 | } |
| 50 | (&mut arr[start..][..end]).copy_from_slice(bucket.as_slice()); |
| 51 | start += end; |
| 52 | } |
| 53 | for bucket in buckets.iter() { |
| 54 | if pivot != 0 { |
| 55 | break; |
| 56 | } |
| 57 | pivot += bucket.len(); |
| 58 | } |
| 59 | if pivot < arr.len() || cand1 == 0 { |
| 60 | pivot |
| 61 | } else { |
| 62 | cand1 |
| 63 | } |
| 64 | } |
| 65 | fn calc_min_and_max(pixels: &[Pixel]) -> (Pixel, Pixel) { |
| 66 | let mut max = Pixel{ r: 0, g: 0, b: 0 }; |
| 67 | let mut min = Pixel{ r: 255, g: 255, b: 255 }; |
| 68 | for pix in pixels.iter() { |
| 69 | max = max.max(*pix); |
| 70 | min = min.min(*pix); |
| 71 | } |
| 72 | (min, max) |
| 73 | } |
| 74 | fn split(self) -> (VQBox<'a>, VQBox<'a>) { |
| 75 | let dr = self.max.r - self.min.r; |
| 76 | let dg = self.max.g - self.min.g; |
| 77 | let db = self.max.b - self.min.b; |
| 78 | |
| 79 | let box0; |
| 80 | let box1; |
| 81 | if (dr > dg) && (dr >= db) { |
| 82 | let pivot = Self::sort(self.pixels, |pix| pix.r as usize); |
| 83 | let (part0, part1) = self.pixels.split_at_mut(pivot); |
| 84 | let (min0, max0) = Self::calc_min_and_max(part0); |
| 85 | let (min1, max1) = Self::calc_min_and_max(part1); |
| 86 | box0 = VQBox { pixels: part0, max: max0, min: min0 }; |
| 87 | box1 = VQBox { pixels: part1, max: max1, min: min1 }; |
| 88 | } else if (db > dr) && (db > dg) { |
| 89 | let pivot = Self::sort(self.pixels, |pix| pix.b as usize); |
| 90 | let (part0, part1) = self.pixels.split_at_mut(pivot); |
| 91 | let (min0, max0) = Self::calc_min_and_max(part0); |
| 92 | let (min1, max1) = Self::calc_min_and_max(part1); |
| 93 | box0 = VQBox { pixels: part0, max: max0, min: min0 }; |
| 94 | box1 = VQBox { pixels: part1, max: max1, min: min1 }; |
| 95 | } else { |
| 96 | let pivot = Self::sort(self.pixels, |pix| pix.g as usize); |
| 97 | let (part0, part1) = self.pixels.split_at_mut(pivot); |
| 98 | let (min0, max0) = Self::calc_min_and_max(part0); |
| 99 | let (min1, max1) = Self::calc_min_and_max(part1); |
| 100 | box0 = VQBox { pixels: part0, max: max0, min: min0 }; |
| 101 | box1 = VQBox { pixels: part1, max: max1, min: min1 }; |
| 102 | } |
| 103 | (box0, box1) |
| 104 | } |
| 105 | } |
| 106 | |
| 107 | pub fn quantise_median_cut(src: &[Pixel], pal: &mut [[u8; 3]; 256]) -> usize { |
| 108 | let mut pixels = Vec::with_capacity(src.len()); |
| 109 | pixels.extend_from_slice(src); |
| 110 | VQBox::sort(pixels.as_mut_slice(), |pix| pix.r as usize); |
| 111 | VQBox::sort(pixels.as_mut_slice(), |pix| pix.g as usize); |
| 112 | VQBox::sort(pixels.as_mut_slice(), |pix| pix.b as usize); |
| 113 | let box0 = VQBox::new(pixels.as_mut_slice()); |
| 114 | let mut boxes: Vec<VQBox> = Vec::with_capacity(256); |
| 115 | boxes.push(box0); |
| 116 | let mut changed = true; |
| 117 | while changed && boxes.len() < 256 { |
| 118 | let end = boxes.len(); |
| 119 | changed = false; |
| 120 | let mut split_largest = false; |
| 121 | for _ in 0..end { |
| 122 | let curbox = boxes.remove(0); |
| 123 | if curbox.can_split() { |
| 124 | let (box0, box1) = curbox.split(); |
| 125 | boxes.push(box0); |
| 126 | boxes.push(box1); |
| 127 | changed = true; |
| 128 | } else { |
| 129 | boxes.push(curbox); |
| 130 | split_largest = true; |
| 131 | break; |
| 132 | } |
| 133 | if boxes.len() == 256 { |
| 134 | break; |
| 135 | } |
| 136 | } |
| 137 | if split_largest { |
| 138 | let mut maxidx = 0; |
| 139 | let mut lcount = 0; |
| 140 | for (i, cbox) in boxes.iter().enumerate() { |
| 141 | if cbox.can_split() && cbox.pixels.len() > lcount { |
| 142 | lcount = cbox.pixels.len(); |
| 143 | maxidx = i; |
| 144 | } |
| 145 | } |
| 146 | if lcount > 0 { |
| 147 | let curbox = boxes.remove(maxidx); |
| 148 | let (box0, box1) = curbox.split(); |
| 149 | boxes.push(box0); |
| 150 | boxes.push(box1); |
| 151 | changed = true; |
| 152 | } |
| 153 | } |
| 154 | } |
| 155 | for (curbox, palentry) in boxes.iter().zip(pal.iter_mut()) { |
| 156 | palentry[0] = avg_u8(curbox.min.r, curbox.max.r); |
| 157 | palentry[1] = avg_u8(curbox.min.g, curbox.max.g); |
| 158 | palentry[2] = avg_u8(curbox.min.b, curbox.max.b); |
| 159 | } |
| 160 | |
| 161 | boxes.len() |
| 162 | } |