lua 把图片转换成base64

调用实例

require("ZZBase64")
local files
local file = io.open("E:\\2342.jpg","rb")

if file then
    print "发现文件"
    files = file:read("*a")
    file:close()
else
    print "没有找到文件"
end

--图片转成base64文本
print(ZZBase64.encode(files))

帮助类

ZZBase64 = {}
local string = string

ZZBase64.__code = {
    'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P',
    'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f',
    'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v',
    'w', 'x', 'y', 'z', '', '', '', '', '', '', '', '', '', '', '+', '/',
};
ZZBase64.__decode = {}
for k,v in pairs(ZZBase64.__code) do
    ZZBase64.__decode[string.byte(v,)] = k -
end

function ZZBase64.encode(text)
    local len = string.len(text)
    local left = len %
    len = len - left
    local res = {}
    local index  =
    for i = , len,  do
        local a = string.byte(text, i )
        local b = string.byte(text, i + )
        local c = string.byte(text, i + )
        -- num = a<<16 + b<<8 + c
        local num = a *  + b *  + c
        for j = ,  do
            --tmp = num >> ((4 -j) * 6)
            local tmp = math.floor(num / ( ^ ((-j) * )))
            --curPos = tmp&0x3f
            local curPos = tmp %  +
            res[index] = ZZBase64.__code[curPos]
            index = index +
        end
    end

    if left ==  then
        ZZBase64.__left1(res, index, text, len)
    elseif left ==  then
        ZZBase64.__left2(res, index, text, len)
    end
    return table.concat(res)
end

function ZZBase64.__left2(res, index, text, len)
    local num1 = string.byte(text, len + )
    num1 = num1 *  --lshift 10
    local num2 = string.byte(text, len + )
    num2 = num2 *  --lshift 2
    local num = num1 + num2

    local tmp1 = math.floor(num / ) --rShift 12
    local curPos = tmp1 %  +
    res[index] = ZZBase64.__code[curPos]

    local tmp2 = math.floor(num / )
    curPos = tmp2 %  +
    res[index + ] = ZZBase64.__code[curPos]

    curPos = num %  +
    res[index + ] = ZZBase64.__code[curPos]

    res[index + ] = "="
end

function ZZBase64.__left1(res, index,text, len)
    local num = string.byte(text, len + )
    num = num * 

    tmp = math.floor(num / )
    local curPos = tmp %  +
    res[index ] = ZZBase64.__code[curPos]

    curPos = num %  +
    res[index + ] = ZZBase64.__code[curPos]

    res[index + ] = "="
    res[index + ] = "="
end

function ZZBase64.decode(text)
    local len = string.len(text)
    local left =
    if string.sub(text, len - ) == "==" then
        left =
        len = len -
    elseif string.sub(text, len) == "=" then
        left =
        len = len -
    end

    local res = {}
    local index =
    local decode = ZZBase64.__decode
    for i =, len,  do
        local a = decode[string.byte(text,i    )]
        local b = decode[string.byte(text,i + )]
        local c = decode[string.byte(text,i + )]
        local d = decode[string.byte(text,i + )]

        --num = a<<18 + b<<12 + c<<6 + d
        local num = a *  + b *  + c *  + d

        local e = string.char(num % )
        num = math.floor(num / )
        local f = string.char(num % )
        num = math.floor(num / )
        res[index ] = string.char(num % )
        res[index + ] = f
        res[index + ] = e
        index = index +
    end

    if left ==  then
        ZZBase64.__decodeLeft1(res, index, text, len)
    elseif left ==  then
        ZZBase64.__decodeLeft2(res, index, text, len)
    end
    return table.concat(res)
end

function ZZBase64.__decodeLeft1(res, index, text, len)
    local decode = ZZBase64.__decode
    local a = decode[string.byte(text, len + )]
    local b = decode[string.byte(text, len + )]
    local c = decode[string.byte(text, len + )]
    local num = a *  + b *  + c

    local num1 = math.floor(num / ) %
    local num2 = math.floor(num / ) %
    res[index] = string.char(num1)
    res[index + ] = string.char(num2)
end

function ZZBase64.__decodeLeft2(res, index, text, len)
    local decode = ZZBase64.__decode
    local a = decode[string.byte(text, len + )]
    local b = decode[string.byte(text, len + )]
    local num = a *  + b
    num = math.floor(num / )
    res[index] = string.char(num)
end