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support returning color index and transparency of paletted images #1

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support returning color index and transparency of paletted images #1

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24 changes: 19 additions & 5 deletions png.lua
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Original file line number Diff line number Diff line change
Expand Up @@ -96,12 +96,23 @@ local function getDataPLTE(stream, length)
data.colors[i] = {
R = readByte(stream),
G = readByte(stream),
B = readByte(stream)
B = readByte(stream),
A = 255
}
end
return data
end

local function getDatatRNS(stream, length, palette)
local data = {}
data["numColors"] = length
data["colors"] = {}
for i = 1, length do
palette.colors[i].A = readByte(stream)
end
return data
end

local function extractChunkData(stream)
local chunkData = {}
local length
Expand All @@ -116,7 +127,9 @@ local function extractChunkData(stream)
elseif (type == "IDAT") then
chunkData[type] = getDataIDAT(stream, length, chunkData[type])
elseif (type == "PLTE") then
chunkData[type] = getDataPLTE(stream, length)
chunkData[type] = getDataPLTE(stream, length)
elseif (type == "tRNS") then
chunkData[type] = getDatatRNS(stream, length, chunkData["PLTE"])
else
readChar(stream, length)
end
Expand All @@ -128,7 +141,7 @@ end

local function makePixel(stream, depth, colorType, palette)
local bps = math.floor(depth/8) --bits per sample
local pixelData = { R = 0, G = 0, B = 0, A = 0 }
local pixelData = { R = 0, G = 0, B = 0, A = 0, I = 0 }
local grey
local index
local color
Expand All @@ -150,7 +163,8 @@ local function makePixel(stream, depth, colorType, palette)
pixelData.R = color.R
pixelData.G = color.G
pixelData.B = color.B
pixelData.A = 255
pixelData.A = color.A
pixelData.I = index
elseif colorType == 4 then
grey = readInt(stream, bps)
pixelData.R = grey
Expand Down Expand Up @@ -303,4 +317,4 @@ local function pngImage(path, progCallback, verbose, memSave)
}
end

return pngImage
return pngImage