diff options
| -rw-r--r-- | adapter/img/sixel.nim | 75 |
1 files changed, 58 insertions, 17 deletions
diff --git a/adapter/img/sixel.nim b/adapter/img/sixel.nim index 12686288..d34f8cf8 100644 --- a/adapter/img/sixel.nim +++ b/adapter/img/sixel.nim @@ -1,7 +1,9 @@ # Sixel codec. I'm lazy, so no decoder yet. # # "Regular" mode just encodes the image as a sixel image, with -# Cha-Image-Sixel-Palette colors. (TODO: maybe adjust this based on quality?) +# Cha-Image-Sixel-Palette colors. If that isn't given, it's set +# according to Cha-Image-Quality. +# # The encoder also has a "half-dump" mode, where the output is modified as # follows: # @@ -213,32 +215,60 @@ type d1: seq[DitherDiff] d2: seq[DitherDiff] +proc getColor(nodes: seq[Node]; c: RGBColor; diff: var DitherDiff): Node = + var child: Node = nil + var minDist = uint32.high + for node in nodes: + let ic = node.c + let rd = int32(c.r) - int32(ic.r) + let gd = int32(c.g) - int32(ic.g) + let bd = int32(c.b) - int32(ic.b) + let d = uint32(abs(rd)) + uint32(abs(gd)) + uint32(abs(bd)) + if d < minDist: + minDist = d + child = node + diff = (rd, gd, bd) + if ic == c: + break + return child + proc getColor(node: Node; c: RGBColor; nodes: seq[Node]; diff: var DitherDiff; - level = 0): Node = + level: int): Node = if node.leaf: - let r = int32(c.r) - int32(node.c.r) - let g = int32(c.g) - int32(node.c.g) - let b = int32(c.b) - int32(node.c.b) + let ic = node.c + let r = int32(c.r) - int32(ic.r) + let g = int32(c.g) - int32(ic.g) + let b = int32(c.b) - int32(ic.b) diff = (r, g, b) return node let idx = int(c.getIdx(level)) var child = node.children[idx] let nlevel = level + 1 if child == nil: - var minDist = uint32.high - for node in nodes: - let rd = int32(c.r) - int32(node.c.r) - let gd = int32(c.g) - int32(node.c.g) - let bd = int32(c.b) - int32(node.c.b) - let d = uint32(abs(rd)) + uint32(abs(gd)) + uint32(abs(bd)) - if d < minDist: - minDist = d - child = node - diff = (rd, gd, bd) + let child = nodes.getColor(c, diff) node.children[idx] = child return child return child.getColor(c, nodes, diff, nlevel) +proc getColor(node: Node; c: RGBColor; nodes: seq[Node]; diff: var DitherDiff): + int = + if nodes.len < 63: + # Octree-based nearest neighbor search creates really ugly artifacts + # with a low amount of colors, which is exactly the case where + # linear search is still acceptable. + # + # 64 is the first power of 2 that gives OK results on my test images + # with the octree; we must also subtract one for transparency. + # + # (In practice, I assume no sane terminal would pick a palette (> 2) + # that isn't a multiple of 4, so really only 16 is relevant here. + # Even that is quite rare, unless you misconfigure XTerm - or + # have a hardware terminal, but those didn't have private color + # registers in the first place. I do like the aesthetics, though; + # would be a shame if it didn't work :P) + return nodes.getColor(c, diff).idx + return node.getColor(c, nodes, diff, 0).idx + proc correctDither(c: RGBColor; x: int; dither: Dither): RGBColor = let (rd, gd, bd) = dither.d1[x + 1] let r = uint8(clamp(int32(c.r) + rd div 16, 0, 100)) @@ -364,7 +394,7 @@ proc encode(s: string; width, height, offx, offy, cropw: int; halfdump: bool; let m = n + (offx + j) * 4 let c0 = s.getPixel(m, bgcolor).correctDither(j, dither) var diff: DitherDiff - let c = node.getColor(c0, nodes, diff).idx + let c = node.getColor(c0, nodes, diff) dither.fs(j, diff) if chunk == nil or chunk.c != c: chunk = addr chunkMap[c - 1] @@ -445,6 +475,7 @@ proc main() = var palette = -1 var bgcolor = rgb(0, 0, 0) var cropw = -1 + var quality = -1 for hdr in headers.split('\n'): let s = hdr.after(':').strip() case hdr.until(':') @@ -464,12 +495,22 @@ proc main() = if q.isNone: die("Cha-Control: ConnectionError 1 wrong palette\n") palette = int(q.get) + of "Cha-Image-Quality": + let q = parseUInt16(s, allowSign = false) + if q.isNone: + die("Cha-Control: ConnectionError 1 wrong quality\n") + quality = int(q.get) of "Cha-Image-Background-Color": bgcolor = parseLegacyColor0(s) if cropw == -1: cropw = width if palette == -1: - palette = 16 + if quality < 30: + palette = 16 + elif quality < 70: + palette = 256 + else: + palette = 1024 if width == 0 or height == 0: puts("Cha-Image-Dimensions: 0x0\n") quit(0) # done... |