cocos,截图分享，截取屏幕某一位置

因为需要做个屏幕固定位置的分享功能，做了一个小demo，

实现思路两步步

1、renderTexture接口截取固定位置

2、保存到沙盒本地

3、预留精灵返回值

以下就是具体实现

--[[ 

    截屏函数
    targetNode：截取父节点
    size：图片尺寸
    viewports:截取位置信息

--[[ 
function GD.util_createScreenSprite(targetNode, size, viewports)

    local winSize = size or cc.Director:getInstance():getWinSize()

    local width = size ~= nil and size.width or winSize.width

    local height = size ~= nil and size.height or winSize.height

    local renderTexture = cc.RenderTexture:create(width, height, cc.TEXTURE2_D_PIXEL_FORMAT_RGB_A8888, gl.DEPTH24_STENCIL8_OES)



    if viewports then
        renderTexture:setVirtualViewport(viewports.rtBegin, viewports.fullRect, viewports.fullViewport)
    end

    renderTexture:begin()
    if targetNode then
        targetNode:visit()
    else
        cc.Director:getInstance():getRunningScene():visit()
    end
    rend