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simpler

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This commit is contained in:
Ryan Oldenburg 2022-05-16 18:08:18 -05:00
parent a21de1d55a
commit 34fa05da97
1 changed files with 15 additions and 32 deletions
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41
src/pixie/fileformats/jpeg.nim
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@ -474,9 +474,8 @@ proc decodeRegularBlock(
) = ) =
## Decodes a whole block. ## Decodes a whole block.
let t = state.huffmanDecode(0, state.components[component].huffmanDC).int let t = state.huffmanDecode(0, state.components[component].huffmanDC).int
if t < 0: if t > 15:
failInvalid() failInvalid("bad huffman code")
let let
diff = diff =
if t == 0: if t == 0:
@ -488,7 +487,7 @@ proc decodeRegularBlock(
data[0] = cast[int16](dc) data[0] = cast[int16](dc)
var i = 1 var i = 1
while true: while i < 64:
let let
rs = state.huffmanDecode(1, state.components[component].huffmanAC) rs = state.huffmanDecode(1, state.components[component].huffmanAC)
s = rs and 15 s = rs and 15
@ -499,15 +498,12 @@ proc decodeRegularBlock(
i += 16 i += 16
else: else:
i += r.int i += r.int
if i notin 0 ..< 64: if i >= 64:
failInvalid() failInvalid()
let zig = deZigZag[i] let zig = deZigZag[i]
data[zig] = cast[int16](state.getBitsAsSignedInt(s.int)) data[zig] = cast[int16](state.getBitsAsSignedInt(s.int))
inc i inc i
if not(i < 64):
break
proc decodeProgressiveBlock( proc decodeProgressiveBlock(
state: var DecoderState, component: int, data: var array[64, int16] state: var DecoderState, component: int, data: var array[64, int16]
) = ) =
@ -517,18 +513,17 @@ proc decodeProgressiveBlock(
if state.successiveApproxHigh == 0: if state.successiveApproxHigh == 0:
let t = state.huffmanDecode(0, state.components[component].huffmanDC).int let t = state.huffmanDecode(0, state.components[component].huffmanDC).int
if t < 0 or t > 15: if t > 15:
failInvalid() failInvalid("bad huffman code")
let let
diff = if t != 0: diff =
if t > 0:
state.getBitsAsSignedInt(t) state.getBitsAsSignedInt(t)
else: else:
0 0
let
dc = state.components[component].dcPred + diff dc = state.components[component].dcPred + diff
state.components[component].dcPred = dc state.components[component].dcPred = dc
data[0] = cast[int16](dc * (1 shl state.successiveApproxLow)) data[0] = cast[int16](dc * (1 shl state.successiveApproxLow))
else: else:
if getBit(state) != 0: if getBit(state) != 0:
data[0] = cast[int16](data[0] + (1 shl state.successiveApproxLow)) data[0] = cast[int16](data[0] + (1 shl state.successiveApproxLow))
@ -548,12 +543,9 @@ proc decodeProgressiveContinuationBlock(
return return
var k = state.spectralStart var k = state.spectralStart
while true: while k <= state.spectralEnd:
let let
rs = state.huffmanDecode(1, state.components[component].huffmanAC) rs = state.huffmanDecode(1, state.components[component].huffmanAC)
if rs < 0:
failInvalid("bad huffman code")
let
s = rs and 15 s = rs and 15
r = rs.int shr 4 r = rs.int shr 4
if s == 0: if s == 0:
@ -566,7 +558,7 @@ proc decodeProgressiveContinuationBlock(
k += 16 k += 16
else: else:
k += r.int k += r.int
if k notin 0 ..< 64: if k >= 64:
failInvalid() failInvalid()
let zig = deZigZag[k] let zig = deZigZag[k]
inc k inc k
@ -574,9 +566,6 @@ proc decodeProgressiveContinuationBlock(
failInvalid() failInvalid()
data[zig] = cast[int16](state.getBitsAsSignedInt(s.int) * (1 shl shift)) data[zig] = cast[int16](state.getBitsAsSignedInt(s.int) * (1 shl shift))
if not(k <= state.spectralEnd):
break
else: else:
var bit = 1 shl state.successiveApproxLow var bit = 1 shl state.successiveApproxLow
@ -593,11 +582,8 @@ proc decodeProgressiveContinuationBlock(
data[zig] = cast[int16](data[zig] - bit) data[zig] = cast[int16](data[zig] - bit)
else: else:
var k = state.spectralStart var k = state.spectralStart
while true: while k <= state.spectralEnd:
let let rs = state.huffmanDecode(1, state.components[component].huffmanAC)
rs = state.huffmanDecode(1, state.components[component].huffmanAC)
if rs < 0:
failInvalid("bad huffman code")
var var
s = rs.int and 15 s = rs.int and 15
r = rs.int shr 4 r = rs.int shr 4
@ -633,9 +619,6 @@ proc decodeProgressiveContinuationBlock(
break break
dec r dec r
if not (k <= state.spectralEnd):
break
template idct1D(s0, s1, s2, s3, s4, s5, s6, s7: int32) = template idct1D(s0, s1, s2, s3, s4, s5, s6, s7: int32) =
## Inverse discrete cosine transform 1D ## Inverse discrete cosine transform 1D
template f2f(x: float32): int32 = (x * 4096 + 0.5).int32 template f2f(x: float32): int32 = (x * 4096 + 0.5).int32