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shrink overflow+range checks off to just idct

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This commit is contained in:
Ryan Oldenburg 2022-05-12 18:55:22 -05:00
parent 35efcf1495
commit 07ec93a7ef
1 changed files with 16 additions and 16 deletions
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32
src/pixie/fileformats/jpeg.nim
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@ -472,8 +472,6 @@ proc getBitsAsUnsignedInt(state: var DecoderState, n: int): int =
state.bitCount -= n
return k.int
{.push overflowChecks: off, rangeChecks: off.}
proc decodeRegularBlock(
state: var DecoderState, component: int, data: var array[64, int16]
) =
@ -489,7 +487,7 @@ proc decodeRegularBlock(
state.getBitsAsSignedInt(t)
dc = state.components[component].dcPred + diff
state.components[component].dcPred = dc
data[0] = dc.int16
data[0] = cast[int16](dc)
var i = 1
while true:
@ -506,7 +504,7 @@ proc decodeRegularBlock(
if i notin 0 ..< 64:
failInvalid()
let zig = deZigZag[i]
data[zig] = state.getBitsAsSignedInt(s.int).int16
data[zig] = cast[int16](state.getBitsAsSignedInt(s.int))
inc i
if not(i < 64):
@ -531,11 +529,11 @@ proc decodeProgressiveBlock(
let
dc = state.components[component].dcPred + diff
state.components[component].dcPred = dc
data[0] = (dc * (1 shl state.successiveApproxLow)).int16
data[0] = cast[int16](dc * (1 shl state.successiveApproxLow))
else:
if getBit(state) != 0:
data[0] += (1 shl state.successiveApproxLow).int16
data[0] = cast[int16](data[0] + (1 shl state.successiveApproxLow))
proc decodeProgressiveContinuationBlock(
state: var DecoderState, component: int, data: var array[64, int16]
@ -576,7 +574,7 @@ proc decodeProgressiveContinuationBlock(
inc k
if s >= 15:
failInvalid()
data[zig] = (state.getBitsAsSignedInt(s.int) * (1 shl shift)).int16
data[zig] = cast[int16](state.getBitsAsSignedInt(s.int) * (1 shl shift))
if not(k <= state.spectralEnd):
break
@ -592,9 +590,9 @@ proc decodeProgressiveContinuationBlock(
if state.getBit() != 0:
if (data[zig] and bit) == 0:
if data[zig] > 0:
data[zig] += bit.int16
data[zig] = cast[int16](data[zig] + bit)
else:
data[zig] -= bit.int16
data[zig] = cast[int16](data[zig] - bit)
else:
var k = state.spectralStart
while true:
@ -628,12 +626,12 @@ proc decodeProgressiveContinuationBlock(
if getBit(state) != 0:
if (data[zig] and bit) == 0:
if data[zig] > 0:
data[zig] += bit.int16
data[zig] = cast[int16](data[zig] + bit)
else:
data[zig] -= bit.int16
data[zig] = cast[int16](data[zig] - bit)
else:
if r == 0:
data[zig] = s.int16
data[zig] = cast[int16](s)
break
dec r
@ -679,6 +677,8 @@ template idct1D(s0, s1, s2, s3, s4, s5, s6, s7: int32) =
t1 += p2 + p4
t0 += p1 + p3
{.push overflowChecks: off, rangeChecks: off.}
proc idctBlock(component: var Component, offset: int, data: array[64, int16]) =
## Inverse discrete cosine transform whole block.
var values: array[64, int32]
@ -755,6 +755,8 @@ proc idctBlock(component: var Component, offset: int, data: array[64, int16]) =
component.channel.data[outPos + 3] = clampByte((x3 + t0) shr 17)
component.channel.data[outPos + 4] = clampByte((x3 - t0) shr 17)
{.pop.}
proc decodeBlock(state: var DecoderState, comp, row, column: int) =
## Decodes a block.
var data {.byaddr.} = state.components[comp].blocks[row][column]
@ -819,9 +821,9 @@ proc quantizationAndIDCTPass(state: var DecoderState) =
for i in 0 ..< 64:
let qTableId = state.components[comp].quantizationTableId
if qTableId.int notin 0 ..< state.quantizationTables.len:
if qTableId.int >= state.quantizationTables.len:
failInvalid()
data[i] = data[i] * state.quantizationTables[qTableId][i].int16
data[i] = cast[int16](data[i] * state.quantizationTables[qTableId][i].int32)
state.components[comp].idctBlock(
state.components[comp].widthStride * column * 8 + row * 8,
@ -888,8 +890,6 @@ proc grayScaleToRgbx(gray: uint8): ColorRGBX =
result.b = g
result.a = 255
{.pop.}
proc buildImage(state: var DecoderState): Image =
## Takes a jpeg image object and builds a pixie Image from it.