Implement a proper clampbits

The C++ conversion to rust was just broken. Implement it naively and maybe later we can find a fast way of doing it.
dnglab · Nov 2, 2020 · 46d5208 · 46d5208
1 parent e93e0db
commit 46d5208
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Showing 4 changed files with 23 additions and 22 deletions.
diff --git a/src/decoders/basics.rs b/src/decoders/basics.rs
@@ -4,12 +4,13 @@ use rayon::prelude::*;
 pub use crate::decoders::packed::*;
 pub use crate::decoders::pumps::*;
 
-pub fn clampbits(val: i32, bits: u32) -> i32 {
-  let temp = val >> bits;
-  if temp != 0 {
-    !temp >> (32-bits)
+pub fn clampbits(val: i32, bits: u32) -> u16 {
+  if val < 0 {
+    0
+  } else if val > (1 << bits) {
+    1 << bits
   } else {
-    val
+    val as u16
   }
 }
 

diff --git a/src/decoders/cr2.rs b/src/decoders/cr2.rs
@@ -196,9 +196,9 @@ impl<'a> Cr2Decoder<'a> {
       let g = c2 * (y + ((-778*cb - (cr<<11)) >> 12));
       let b = c3 * (y + cb);
 
-      pix[0] = clampbits(r >> 8, 16) as u16;
-      pix[1] = clampbits(g >> 8, 16) as u16;
-      pix[2] = clampbits(b >> 8, 16) as u16;
+      pix[0] = clampbits(r >> 8, 16);
+      pix[1] = clampbits(g >> 8, 16);
+      pix[2] = clampbits(b >> 8, 16);
     }
     Ok(())
   }

diff --git a/src/decoders/nef.rs b/src/decoders/nef.rs
@@ -56,7 +56,7 @@ lazy_static! {
       } else {
         ((v+f)/(1.0+f)).powf(g)
       };
-      clampbits((res*65535.0*4.0) as i32, 16) as u16
+      clampbits((res*65535.0*4.0) as i32, 16)
     }).collect::<Vec<u16>>();
     LookupTable::new(&curve)
   };
@@ -324,8 +324,8 @@ impl<'a> NefDecoder<'a> {
           pred_left1 += htable.huff_decode_nef(&mut pump)?;
           pred_left2 += htable.huff_decode_nef(&mut pump)?;
         }
-        out[row*width+col+0] = curve.dither(clampbits(pred_left1,15) as u16, &mut random);
-        out[row*width+col+1] = curve.dither(clampbits(pred_left2,15) as u16, &mut random);
+        out[row*width+col+0] = curve.dither(clampbits(pred_left1,14), &mut random);
+        out[row*width+col+1] = curve.dither(clampbits(pred_left2,14), &mut random);
       }
     }
 
@@ -356,21 +356,21 @@ impl<'a> NefDecoder<'a> {
         let cb = (g4 | ((g5 & 0x0f) << 8)) as f32 - 2048.0;
         let cr = ((g5 >> 4) | (g6 << 4)) as f32 - 2048.0;
 
-        let r = SNEF_CURVE.dither(clampbits((y1 + 1.370705 * cr) as i32, 12) as u16, &mut random);
-        let g = SNEF_CURVE.dither(clampbits((y1 - 0.337633 * cb - 0.698001 * cr) as i32, 12) as u16, &mut random);
-        let b = SNEF_CURVE.dither(clampbits((y1 + 1.732446 * cb) as i32, 12) as u16, &mut random);
+        let r = SNEF_CURVE.dither(clampbits((y1 + 1.370705 * cr) as i32, 12), &mut random);
+        let g = SNEF_CURVE.dither(clampbits((y1 - 0.337633 * cb - 0.698001 * cr) as i32, 12), &mut random);
+        let b = SNEF_CURVE.dither(clampbits((y1 + 1.732446 * cb) as i32, 12), &mut random);
         // invert the white balance
-        o[0] = clampbits((inv_wb_r * r as i32 + (1<<9)) >> 10, 15) as u16;
+        o[0] = clampbits((inv_wb_r * r as i32 + (1<<9)) >> 10, 15);
         o[1] = g;
-        o[2] = clampbits((inv_wb_b * b as i32 + (1<<9)) >> 10, 15) as u16;
+        o[2] = clampbits((inv_wb_b * b as i32 + (1<<9)) >> 10, 15);
 
-        let r = SNEF_CURVE.dither(clampbits((y2 + 1.370705 * cr) as i32, 12) as u16, &mut random);
-        let g = SNEF_CURVE.dither(clampbits((y2 - 0.337633 * cb - 0.698001 * cr) as i32, 12) as u16, &mut random);
-        let b = SNEF_CURVE.dither(clampbits((y2 + 1.732446 * cb) as i32, 12) as u16, &mut random);
+        let r = SNEF_CURVE.dither(clampbits((y2 + 1.370705 * cr) as i32, 12), &mut random);
+        let g = SNEF_CURVE.dither(clampbits((y2 - 0.337633 * cb - 0.698001 * cr) as i32, 12), &mut random);
+        let b = SNEF_CURVE.dither(clampbits((y2 + 1.732446 * cb) as i32, 12), &mut random);
         // invert the white balance
-        o[3] = clampbits((inv_wb_r * r as i32 + (1<<9)) >> 10, 15) as u16;
+        o[3] = clampbits((inv_wb_r * r as i32 + (1<<9)) >> 10, 15);
         o[4] = g;
-        o[5] = clampbits((inv_wb_b * b as i32 + (1<<9)) >> 10, 15) as u16;
+        o[5] = clampbits((inv_wb_b * b as i32 + (1<<9)) >> 10, 15);
       }
     }))
   }

diff --git a/src/decoders/srw.rs b/src/decoders/srw.rs
@@ -366,7 +366,7 @@ impl<'a> SrwDecoder<'a> {
           } else {
             ((i&0x7) << 1) + (i>>3)
           } + img + col;
-          out[pos] = clampbits((out[pos] as i32) + diff, bit_depth) as u16;
+          out[pos] = clampbits((out[pos] as i32) + diff, bit_depth);
         }
       }
     }