clean up

src/pixie/fileformats/jpeg.nim

@@ -103,10 +103,6 @@ template clampByte(x): uint8 =
   ## Clamp integer into byte range.
   clamp(x, 0, 0xFF).uint8
 
-template clampInt16(x): int16 =
-  ## Clamp integer into byte range.
-  clamp(x, -32768, 32767).int16
-
 proc readUint8(state: var DecoderState): uint8 =
   ## Reads a byte from the input stream.
   if state.pos >= state.buffer.len:
@@ -243,8 +239,8 @@ proc decodeSOF0(state: var DecoderState) =
     failInvalid("unsupported component count, must be 1 or 3")
 
   for i in 0 ..< numComponents:
-    state.components.add(Component())
-    state.components[i].id = state.readUint8()
+    var component = Component()
+    component.id = state.readUint8()
     let
       info = state.readUint8()
       vertical = info and 15
@@ -257,18 +253,19 @@ proc decodeSOF0(state: var DecoderState) =
     if vertical == 0 or vertical > 4 or horizontal == 0 or horizontal > 4:
       failInvalid("invalid component scaling factor")
 
-    state.components[i].xScale = vertical.int
-    state.components[i].yScale = horizontal.int
-    state.components[i].quantizationTableId = quantizationTableId
+    component.xScale = vertical.int
+    component.yScale = horizontal.int
+    component.quantizationTableId = quantizationTableId
+    state.components.add(component)
 
-  for i in 0 ..< state.components.len:
+  for component in state.components.mitems:
     state.maxXScale = max(
       state.maxXScale,
-      state.components[i].xScale
+      component.xScale
     )
     state.maxYScale = max(
       state.maxYScale,
-      state.components[i].yScale
+      component.yScale
     )
 
   state.mcuWidth = state.maxYScale * 8
@@ -278,40 +275,40 @@ proc decodeSOF0(state: var DecoderState) =
   state.numMcuHigh =
     (state.imageHeight + state.mcuHeight - 1) div state.mcuHeight
 
-  for i in 0 ..< state.components.len:
-    state.components[i].width = (
+  for component in state.components.mitems:
+    component.width = (
       state.imageWidth *
-      state.components[i].yScale +
+      component.yScale +
       state.maxYScale - 1
     ) div state.maxYScale
-    state.components[i].height = (
+    component.height = (
       state.imageHeight *
-      state.components[i].xScale +
+      component.xScale +
       state.maxXScale - 1
     ) div state.maxXScale
 
     # Allocate block data structures.
-    state.components[i].blocks = newSeqWith(
-      state.components[i].width,
+    component.blocks = newSeqWith(
+      component.width,
       newSeq[array[64, int16]](
-        state.components[i].height
+        component.height
       )
     )
 
-    state.components[i].widthStride =
-      state.numMcuWide * state.components[i].yScale * 8
-    state.components[i].heightStride =
-      state.numMcuHigh * state.components[i].xScale * 8
+    component.widthStride =
+      state.numMcuWide * component.yScale * 8
+    component.heightStride =
+      state.numMcuHigh * component.xScale * 8
 
-    state.components[i].channel = newMask(
-      state.components[i].widthStride, state.components[i].heightStride
+    component.channel = newMask(
+      component.widthStride, component.heightStride
     )
 
     if state.progressive:
-      state.components[i].widthCoeff = state.components[i].widthStride div 8
-      state.components[i].heightCoeff = state.components[i].heightStride div 8
-      state.components[i].coeff.setLen(
-        state.components[i].widthStride * state.components[i].heightStride
+      component.widthCoeff = component.widthStride div 8
+      component.heightCoeff = component.heightStride div 8
+      component.coeff.setLen(
+        component.widthStride * component.heightStride
       )
 
 proc decodeSOF1(state: var DecoderState) =
@@ -509,7 +506,7 @@ proc decodeRegularBlock(
       state.getBitsAsSignedInt(t)
     dc = state.components[component].dcPred + diff
   state.components[component].dcPred = dc
-  data[0] = clampInt16(dc)
+  data[0] = dc.int16
 
   var i = 1
   while true:
@@ -551,7 +548,7 @@ proc decodeProgressiveBlock(
     let
       dc = state.components[component].dcPred + diff
     state.components[component].dcPred = dc
-    data[0] = clampInt16(dc * (1 shl state.successiveApproxLow))
+    data[0] = (dc * (1 shl state.successiveApproxLow)).int16
 
   else:
     if getBit(state) != 0:
@@ -596,7 +593,7 @@ proc decodeProgressiveContinuationBlock(
         inc k
         if s >= 15:
           failInvalid()
-        data[zig] = clampInt16(state.getBitsAsSignedInt(s.int) * (1 shl shift))
+        data[zig] = (state.getBitsAsSignedInt(s.int) * (1 shl shift)).int16
 
       if not(k <= state.spectralEnd):
         break
@@ -708,7 +705,7 @@ proc idctBlock(component: var Component, offset: int, data: array[64, int16]) =
       data[i + 40] == 0 and
       data[i + 48] == 0 and
       data[i + 56] == 0:
-      let dcterm = clampInt16(data[i].int * 4.int)
+      let dcterm = data[i] * 4
       values[i + 0] = dcterm
       values[i + 8] = dcterm
       values[i + 16] = dcterm
@@ -854,7 +851,7 @@ proc quantizationAndIDCTPass(state: var DecoderState) =
           let qTableId = state.components[comp].quantizationTableId
           if qTableId.int notin 0 ..< state.quantizationTables.len:
             failInvalid()
-          data[i] = clampInt16(data[i] * state.quantizationTables[qTableId][i].int)
+          data[i] = data[i] * state.quantizationTables[qTableId][i].int16
 
         state.components[comp].idctBlock(
           state.components[comp].widthStride * column * 8 + row * 8,