Added takeScreenshot utility. #183

CHANGELOG.md

@@ -4,6 +4,7 @@
 - **[UPDATE]** Updated to Kotlin Coroutines 1.3.5.
 - **[FEATURE]** (`ktx-ashley`) Added `Entity.contains` (`in` operator) that checks if an `Entity` has a `Component`.
 - **[FEATURE]** (`ktx-async`) Added `RenderingScope` factory function for custom scopes using rendering thread dispatcher.
+- **[FEATURE]** (`ktx-graphics`) Added `takeScreenshot` utility function that allows to save a screenshot of the application.
 - **[FEATURE]** (`ktx-math`) Added `lerp` and `interpolate` extension functions for `Float` ranges.
 - **[FEATURE]** (`ktx-preferences`) Added a new KTX module: Preferences API extensions.
     - Added `set` operators for `String`, `Int`, `Float`, `Double`, `Long`, `Boolean`, `Pair<String, Any>` and `Any`

graphics/README.md

@@ -21,6 +21,7 @@ overriding with optional, named parameters.
 `begin()` and `end()` calls when using batches, shader programs and buffers. Note that a camera or projection matrix can
 also be passed to the `Batch.use` extension function to have it automatically applied to the batch's projection matrix.
 - `begin` extension methods that automatically set projection matrix from a `Camera` or `Matrix4` were added to `Batch`.
+- `takeScreenshot` allows to easily take a screenshot of current application screen.
 
 #### `ShapeRenderer`
 
@@ -162,6 +163,14 @@ fun drawCircle(renderer: ShapeRenderer) {
 }
 ```
 
+Taking a screenshot of the current game screen:
+
+```Kotlin
+import ktx.graphics.takeScreenshot
+
+takeScreenshot(Gdx.files.external("mygame/screenshot.png"))
+```
+
 #### Synergy
 
 Use [`ktx-math`](../math) for `Vector2` and `Vector3` extensions, including idiomatic Kotlin factory

graphics/build.gradle

@@ -1,3 +1,5 @@
 dependencies {
-    provided "org.jetbrains.kotlin:kotlin-stdlib:$kotlinVersion"
+  provided "org.jetbrains.kotlin:kotlin-stdlib:$kotlinVersion"
+  testCompile "com.badlogicgames.gdx:gdx-backend-lwjgl:$gdxVersion"
+  testCompile "com.badlogicgames.gdx:gdx-platform:$gdxVersion:natives-desktop"
 }

graphics/src/main/kotlin/ktx/graphics/graphics.kt

@@ -1,11 +1,17 @@
 package ktx.graphics
 
+import com.badlogic.gdx.Gdx
+import com.badlogic.gdx.files.FileHandle
 import com.badlogic.gdx.graphics.Camera
 import com.badlogic.gdx.graphics.Color
+import com.badlogic.gdx.graphics.Pixmap
+import com.badlogic.gdx.graphics.PixmapIO
 import com.badlogic.gdx.graphics.g2d.Batch
 import com.badlogic.gdx.graphics.glutils.GLFrameBuffer
 import com.badlogic.gdx.graphics.glutils.ShaderProgram
 import com.badlogic.gdx.math.Matrix4
+import com.badlogic.gdx.utils.BufferUtils
+import com.badlogic.gdx.utils.ScreenUtils
 
 /**
  * Factory methods for LibGDX [Color] class. Allows to use named parameters.
@@ -82,3 +88,25 @@ inline fun <B : GLFrameBuffer<*>> B.use(action: (B) -> Unit) {
   action(this)
   end()
 }
+
+/**
+ * Takes a screenshot of the entire screen and saves the image using the given [fileHandle].
+ */
+fun takeScreenshot(fileHandle: FileHandle) {
+  val bufferWidth = Gdx.graphics.backBufferWidth
+  val bufferHeight = Gdx.graphics.backBufferHeight
+  val pixels = ScreenUtils.getFrameBufferPixels(0, 0, bufferWidth, bufferHeight, true)
+
+  // Ensuring the screenshot is opaque:
+  var i = 4
+  val alpha = 255.toByte()
+  while (i < pixels.size) {
+    pixels[i - 1] = alpha
+    i += 4
+  }
+
+  val screenshotImage = Pixmap(bufferWidth, bufferHeight, Pixmap.Format.RGBA8888)
+  BufferUtils.copy(pixels, 0, screenshotImage.pixels, pixels.size)
+  PixmapIO.writePNG(fileHandle, screenshotImage)
+  screenshotImage.dispose()
+}

graphics/src/test/kotlin/ktx/graphics/graphicsTest.kt

@@ -1,17 +1,18 @@
 package ktx.graphics
 
+import com.badlogic.gdx.Gdx
+import com.badlogic.gdx.backends.lwjgl.LwjglNativesLoader
+import com.badlogic.gdx.files.FileHandle
 import com.badlogic.gdx.graphics.Color
 import com.badlogic.gdx.graphics.OrthographicCamera
 import com.badlogic.gdx.graphics.g2d.Batch
 import com.badlogic.gdx.graphics.glutils.FrameBuffer
 import com.badlogic.gdx.graphics.glutils.ShaderProgram
 import com.badlogic.gdx.math.Matrix4
-import com.nhaarman.mockitokotlin2.any
-import com.nhaarman.mockitokotlin2.mock
-import com.nhaarman.mockitokotlin2.never
-import com.nhaarman.mockitokotlin2.verify
+import com.nhaarman.mockitokotlin2.*
 import org.junit.Assert.*
 import org.junit.Test
+import java.io.File
 
 /**
  * Tests general utilities related to LibGDX graphics API.
@@ -109,7 +110,7 @@ class GraphicsTest {
   @Test
   fun `should begin with provided projection matrix`() {
     val batch = mock<Batch>()
-    val matrix = Matrix4(FloatArray(16) {it.toFloat()})
+    val matrix = Matrix4(FloatArray(16) { it.toFloat() })
 
     batch.begin(projectionMatrix = matrix)
 
@@ -151,4 +152,19 @@ class GraphicsTest {
     }
     verify(frameBuffer).end()
   }
+
+  @Test
+  fun `should take screenshot`() {
+    LwjglNativesLoader.load()
+    Gdx.gl = mock()
+    Gdx.graphics = mock {
+      on { backBufferHeight } doReturn 4
+      on { backBufferWidth } doReturn 4
+    }
+    val fileHandle = spy(FileHandle(File.createTempFile("screenshot", ".png")))
+
+    takeScreenshot(fileHandle)
+
+    verify(fileHandle).write(false)
+  }
 }