Measuring how long does it take to show an image on CoronaSDK?

Question

I'm working with Corona and I was wonder to know if there is a way to know when an image is totally loaded. I have this code in main.lua:

local widget = require( "widget" )

local function onSystemEvent(event)
    if event.type == "applicationStart" then

        initial = os.clock()
        local myImage = display.newImage("image.jpg", 500, 500)
        final = os.clock()
        time = final - initial; 
        native.showAlert("tiempo ", time )
    end
end

Runtime:addEventListener("system", onSystemEvent)

I want to measure how much time takes to load an image... but the output of my code are like 0,003 seg so I guess what it isn't the really time.

Any idea?

Answer 1

Try screen capture:

local function captureWithDelay()
    local capture = display.captureScreen()
end

timer.performWithDelay( 1, captureWithDelay )

Then read pixel color at last load pixel.

local function onColorSample( event )
    print( "Sampling pixel at position (" .. event.x .. "," .. event.y .. ")" )
    print( "R = " .. event.r )
    print( "G = " .. event.g )
    print( "B = " .. event.b )
    print( "A = " .. event.a )

    print( system.getTimer() )
end

display.colorSample( x, y, onColorSample )

Then compare the results to find out when the color is changed.