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Allow encoding with top-bottom scanline order
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parent
12a33e458f
commit
01bcbbf927
1 changed files with 29 additions and 7 deletions
36
init.lua
36
init.lua
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@ -56,6 +56,11 @@ function image:encode_image_spec(properties)
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"B8G8R8" == color_format or -- (B8G8R8 = 3 bytes = 24 bits)
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"B8G8R8A8" == color_format -- (B8G8R8A8 = 4 bytes = 32 bits)
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)
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local scanline_order = properties.scanline_order
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assert (
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"bottom-top" == scanline_order or
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"top-bottom" == scanline_order
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)
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local pixel_depth
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if 0 ~= #properties.colormap then
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pixel_depth = self.pixel_depth
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@ -63,13 +68,29 @@ function image:encode_image_spec(properties)
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pixel_depth = pixel_depth_by_color_format[color_format]
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end
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assert( nil ~= pixel_depth)
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self.data = self.data
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.. string.char(0, 0) -- X-origin
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.. string.char(0, 0) -- Y-origin
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.. string.char(self.width % 256, math.floor(self.width / 256)) -- width
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.. string.char(self.height % 256, math.floor(self.height / 256)) -- height
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.. string.char(pixel_depth)
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.. string.char(0) -- image descriptor
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-- the origin is the bottom left corner of the image (always)
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local x_origin_lo = 0
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local x_origin_hi = 0
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local y_origin_lo = 0
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local y_origin_hi = 0
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local image_descriptor = 0 -- equal to bottom-top scanline order
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local width_lo = self.width % 256
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local width_hi = math.floor(self.width / 256)
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local height_lo = self.height % 256
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local height_hi = math.floor(self.height / 256)
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if "top-bottom" == scanline_order then
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image_descriptor = 32
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y_origin_lo = height_lo
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y_origin_hi = height_hi
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end
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self.data = self.data .. string.char (
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x_origin_lo, x_origin_hi,
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y_origin_lo, y_origin_hi,
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width_lo, width_hi,
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height_lo, height_hi,
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pixel_depth,
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image_descriptor
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)
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end
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function image:encode_colormap(properties)
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@ -564,6 +585,7 @@ function image:encode(properties)
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local properties = properties or {}
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properties.colormap = properties.colormap or {}
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properties.compression = properties.compression or "RAW"
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properties.scanline_order = properties.scanline_order or "bottom-top"
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self.pixel_depth = #self.pixels[1][1] * 8
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