display.captureScreen()

Type Function
Library display.*
Return value DisplayObject
Revision Current Public Release (2017.3135)
Keywords screenshot, capture screen, save screen
See also display.save()
display.capture()
display.captureBounds()

Overview

Captures the contents of the screen and returns it as a new display object. You can optionally save the capture as a file to the device's photo library.

Calling this method places the captured image on the screen on top of all other display objects. Use object:removeSelf() to remove this object from the screen.

Note

This capture function will only capture what is rendered in OpenGL. It will not capture native display objects such as text input boxes/fields, web popups, ads, etc.

Gotchas

Android

When an app is suspended, the Android OS removes all OpenGL textures from memory. When the app is resumed, Corona must reload all images, but the capture image no longer exists in memory. If you need to restore a captured image in Android, one solution is as follows:

  • Save the returned capture image to file via the display.save() function. Note that you can't use the display.save() function in Android "applicationSuspend" and "applicationExit" events because there are no OpenGL textures in memory to save.
  • Display the image saved to file via display.newImageRect(), using the captured object's bounds.

In addition, if you include the saveToPhotoLibrary option as true, you must set the following permission in the build.settings file:

settings =
{
    android =
    {
        usesPermissions =
        {
            "android.permission.WRITE_EXTERNAL_STORAGE",
        },
    },
}

iOS

On iOS, if you include the saveToPhotoLibrary option as true, you must include the following keys/descriptions in the plist table of build.settings. When the system prompts the user to allow access, the associated description is displayed as part of the alert. Note that these descriptions can be customized to your preference and they can even be localized (guide).

settings =
{
    iphone =
    {
        plist =
        {
            NSPhotoLibraryUsageDescription = "This app would like to access the photo library.",
            NSPhotoLibraryAddUsageDescription = "This app would like to add the photo library.",
        },
    },
}

macOS

Saves screen capture images as JPEG files to the current user's Pictures folder.

Note that if you plan to submit your application to the Mac App Store, it will be sandboxed. This means that special entitlements for read/write files in the Pictures folder must be requested. To do this, simply add an entitlements entry within the settingsosx table of build.settings as indicated below. For further details, see Apple's documentation.

settings = 
{
    osx = {
        entitlements = {
            ["com.apple.security.assets.pictures.read-write"] = true,
        },
    },
}

Windows

Saves screen capture images as PNG files to the user's My Pictures directory under a subdirectory named after the Corona app. For the Corona Simulator, this directory will be My Pictures\Corona Simulator. For Corona-built desktop apps, this directory will be My Pictures\<AppName>.

Capture on Launch

If you need to capture a display object on application launch, for example when main.lua is executed to initialize the app, you must call display.captureScreen() within a timer.performWithDelay() call. A delay of at least 100 milliseconds is recommended.

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

timer.performWithDelay( 100, captureWithDelay )

Syntax

display.captureScreen( [saveToPhotoLibrary] )

saveToPhotoLibrary (optional)

Boolean. If true, then it adds the image to your device's photo library. For Android and iOS devices, this also necessitates the requirements outlined in Gotchas.

Example

-- Fill the screen with a green rectangle
local rect = display.newRect( 0, 0, display.contentWidth, display.contentHeight )
rect:setFillColor( 0, 1, 0.2 )

-- Draw a circle on the screen
local circle = display.newCircle( 155, 100, 36 )
circle:setFillColor( 1, 1, 1, 0.6 )

local function captureOnEvent()

    -- Capture the screen
    local screenCap = display.captureScreen( true )

    -- Remove the objects from the screen
    rect:removeSelf()
    circle:removeSelf()

    -- Scale the screen capture, now on the screen, to half its size
    screenCap:scale( 0.5, 0.5 )
    screenCap.x = display.contentCenterX
    screenCap.y = display.contentCenterY
 
    -- Alert the user to look in the library (device) or on the desktop (Simulator) for the screen capture
    local alert = native.showAlert( "Success", "Screen Capture Saved to Library", { "OK" } )
end

timer.performWithDelay( 500, captureOnEvent )