Unreal Software - Thread: Get baseline jpg/jpeg image width and height

Get baseline jpg/jpeg image width and height

Offline

11.02.14 12:52:01 pm

This time i want to create a script again. I want to create a custom circle function which has radius depending by image size.

radius=math.max(width,height)/2

PNG and BMP image always returns correct value, but i'm getting 1 problem

My script doesn't return correct value when i'm getting baseline jpeg image size(maybe progressive too, but i test it in image 223x223 and it returns correct value). I test it in image which has 320x240 and 800x600 and it always return 120 and 160

Is there a way to get the correct jpg image width & height?

GetImageWidthHeight

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function GetImageWidthHeight(file)
	local fileinfo=type(file)
	if type(file)=="string" then
		file=assert(io.open(file,"rb"))
	else
		fileinfo=file:seek("cur")
	end
	local width,height=0,0
	-- Detect if PNG
	file:seek("set",1)
	if file:read(3)=="PNG" then
		file:seek("set",16)
		local widthstr,heightstr=file:read(4),file:read(4)
		if type(fileinfo)=="number" then
			file:seek("set",fileinfo)
		else
			file:close()
		end
		width=widthstr:sub(1,1):byte()*16777216+widthstr:sub(2,2):byte()*65536+widthstr:sub(3,3):byte()*256+widthstr:sub(4,4):byte()
		height=heightstr:sub(1,1):byte()*16777216+heightstr:sub(2,2):byte()*65536+heightstr:sub(3,3):byte()*256+heightstr:sub(4,4):byte()
		return width,height
	end
	file:seek("set")
	-- Detect if BMP
	if file:read(2)=="BM" then
		file:seek("set",18)
		local widthstr,heightstr=file:read(4),file:read(4)
		if type(fileinfo)=="number" then
			file:seek("set",fileinfo)
		else
			file:close()
		end
		width=widthstr:sub(4,4):byte()*16777216+widthstr:sub(3,3):byte()*65536+widthstr:sub(2,2):byte()*256+widthstr:sub(1,1):byte()
		height=heightstr:sub(4,4):byte()*16777216+heightstr:sub(3,3):byte()*65536+heightstr:sub(2,2):byte()*256+heightstr:sub(1,1):byte()
		return width,height
	end
	-- Detect if JPG/JPEG
	file:seek("set")
	if file:read(2)=="\255\216" then
		-- Search for Progressive/Baseline DCT
		local lastb,curb=0,0
		local sstr=file:read(1)
		while sstr~=nil do
			lastb=curb
			curb=sstr:byte()
			if (curb==194 or curb==192) and lastb==255 then
				file:seek("cur",3)
				local sizestr=file:read(4)
				if type(fileinfo)=="number" then
					file:seek("set",fileinfo)
				else
					file:close()
				end
				width=sizestr:sub(1,1):byte()*256+sizestr:sub(2,2):byte()
				height=sizestr:sub(3,3):byte()*256+sizestr:sub(4,4):byte()
				return width,height
			end
			sstr=file:read(1)
		end
	end
	if type(fileinfo)=="number" then
		file:seek("set",fileinfo)
	else
		file:close()
	end
	return nil
end

And yes it's Exif baseline jpg

Re: Get baseline jpg/jpeg image width and height

Livia
User Off

Offline

11.02.14 02:20:26 pm

I made this quickly and it worked for me.

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function getImageDimensions(filename)
    local file = io.open(filename, "rb")

    file:seek("set")
    if file:read(2) ~= "\255\216" then
        print("not jpg")
        return
    end

    local width = 0
    local height = 0

    -- while not EOF
    while file:read(1)~=nil do
        file:seek("cur", -1)

        -- search for next marker
        while file:read(1) ~= "\xFF" do end
        file:seek("cur", -1)

        -- throw out extra FFs
        while file:read(1) == "\xFF" do end
        file:seek("cur", -1)

        -- read marker
        local byte = file:read(1):byte()

        -- is SOF marker
        if byte >= 192 and byte <= 207 and byte ~= 196 and byte ~= 200 and byte ~= 204 then
            file:seek("cur", 3)

            height = file:read(1):byte()*256+file:read(1):byte()
            width = file:read(1):byte()*256+file:read(1):byte()
            break

        else
            -- read offset and substract 2 bytes we already read
            local offset = file:read(1):byte()*256+file:read(1):byte() - 2

            file:seek("cur", offset)
        end
    end
    file:close()

    return {width, height}
end

Re: Get baseline jpg/jpeg image width and height

MikuAuahDark
User Off

Offline

12.02.14 06:20:42 am

It's very slow(in 17KB of jpg file). I don't have enough time to complete then i press Ctrl+C, so i don't know if it return correct value

Re: Get baseline jpg/jpeg image width and height

Livia
User Off

Offline

12.02.14 07:24:22 am

Sounds like an infinite loop. I think the problem lies on line 18 because it doesn't check EOF.

Re: Get baseline jpg/jpeg image width and height

MikuAuahDark
User Off

Offline

12.02.14 07:41:11 am

If you can't fix it, can you take a look at my code(i give it above) and tell me what's wrong?

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Get baseline jpg/jpeg image width and height