130 lines
3.6 KiB
Lua
130 lines
3.6 KiB
Lua
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local decoders = {}
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local function read_palette_full(palette, fp)
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for i = 1, 16 do
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palette[i] = bit.blshift(string.byte(fp.read(1)), 16)
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palette[i] = bit.bor(palette[i], bit.blshift(string.byte(fp.read(1)), 8))
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palette[i] = bit.bor(palette[i], string.byte(fp.read(1)))
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end
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end
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local function read_pixeldata_v0(image, fp)
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for y = 1, image.h do
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local line = { s = "", bg = "", fg = "" }
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for x = 1, image.w do
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local data = fp.read(2)
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if data == nil or #data == 0 then
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return nil, string.format("Failed to read character at x=%d y=%d", x, y)
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end
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line.s = line.s .. data:sub(1, 1)
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local color = string.byte(data, 2, 2)
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if color == nil then
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return nil, string.format("Failed to read color data for x=%d y=%d", x, y)
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end
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line.bg = line.bg .. string.format("%x", bit.band(0xF, color))
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line.fg = line.fg .. string.format("%x", bit.band(0xF, bit.brshift(color, 4)))
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end
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table.insert(image.lines, line)
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end
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return true
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end
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local function read_varint(fp)
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local value = 0
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local current = 0
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local offset = 0
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repeat
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if offset >= 5 then return nil, "varint too long" end
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current = string.byte(fp.read(1))
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value = bit.bor(value, bit.blshift(bit.band(current, 0x7f), offset * 7))
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offset = offset + 1
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until bit.band(current, 0x80) == 0
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return value
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end
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decoders[0] = function(image, fp)
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image.w, image.h = string.byte(fp.read(1)), string.byte(fp.read(1))
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image.scale = 0.5 + string.byte(fp.read(1)) * 5 / 255
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read_palette_full(image.palette, fp)
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local success, err = read_pixeldata_v0(image, fp)
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if not success then return false, err end
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return true
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end
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decoders[1] = function(image, fp)
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image.w = read_varint(fp)
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image.h = read_varint(fp)
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image.scale = 0.5 -- CPIv1 doesn't have a scale property
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read_palette_full(image.palette, fp)
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local success, err = read_pixeldata_v0(image, fp)
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if not success then return false, err end
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return true
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end
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local function parse(fp)
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local res
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local image = { w = 0, h = 0, scale = 1.0, palette = {}, lines = {} }
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local magic = fp.read(4)
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if magic == "CCPI" then
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res, err = decoders[0](image, fp)
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elseif magic:sub(1, 3) == "CPI" then
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local version = magic:byte(4, 4)
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if decoders[version] == nil then
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return nil, string.format("Invalid CPI version 0x%02x", version)
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end
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res, err = decoders[version](image, fp)
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else
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return nil, "Invalid header: expected CCPI got " .. magic
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end
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if not res then return false, err end
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return image
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end
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local function load(path)
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local fp, err = io.open(path, "rb")
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if not fp then return nil, err end
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local img
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img, err = parse(fp._handle)
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fp:close()
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return img, err
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end
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local function draw(img, ox, oy, monitor)
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-- todo: add expect()
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local t = monitor or term.current()
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ox = ox or 1
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oy = oy or 1
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if not t.setPaletteColor then
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return nil, "setPaletteColor is not supported on this term"
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end
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if not t.setTextScale and img.scale ~= 1 then
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return nil, "setTextScale is not supported on this term"
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end
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for i = 1, 16 do
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t.setPaletteColor(bit.blshift(1, i - 1), img.palette[i])
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end
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if img.scale ~= 1 then
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t.setTextScale(img.scale)
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end
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for y = 1, img.h do
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t.setCursorPos(ox, oy + y - 1)
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t.blit(img.lines[y].s, img.lines[y].fg, img.lines[y].bg)
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end
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end
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return {
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load = load,
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draw = draw,
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parse = parse
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}
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