From 7d7c26758f75c0fa42e768d870ce67931d9e6d02 Mon Sep 17 00:00:00 2001
From: Edwin Jakobs <edwin@rndr.studio>
Date: Mon, 22 Aug 2022 22:22:06 +0200
Subject: [PATCH] Add Post extension

---
 orx-fx/README.md                     |  31 +++++++-
 orx-fx/build.gradle.kts              |   2 +
 orx-fx/src/commonMain/kotlin/Post.kt | 108 +++++++++++++++++++++++++++
 orx-fx/src/demo/kotlin/DemoPost01.kt |  27 +++++++
 4 files changed, 167 insertions(+), 1 deletion(-)
 create mode 100644 orx-fx/src/commonMain/kotlin/Post.kt
 create mode 100644 orx-fx/src/demo/kotlin/DemoPost01.kt

diff --git a/orx-fx/README.md b/orx-fx/README.md
index bdbea16e..46fd7175 100644
--- a/orx-fx/README.md
+++ b/orx-fx/README.md
@@ -108,7 +108,36 @@ All distortion effects are opacity preserving
  ### Transform
   - `FlipVertically` - flips the source input vertically.
  
- 
+## `Post` extension
+
+The `Post` extension provides an easy way to apply filters to your drawings. Allocating
+and resizing color buffers is all taken care of by `Post`.
+
+To get additional intermediate color buffers one can access `intermediate[x]`
+```kotlin
+fun main() = application {
+    configure {
+        windowResizable = true
+    }
+    program {
+        extend(Post()) {
+            val blur = ApproximateGaussianBlur()
+            val add = Add()
+            post { input, output ->
+                blur.window = 50
+                blur.sigma = 50.0
+                blur.apply(input, intermediate[0])
+                add.apply(arrayOf(input, intermediate[0]), output)
+            }
+        }
+        extend {
+            drawer.circle(width / 2.0, height / 2.0, 100.0)
+        }
+    }
+}
+```
+
+
 <!-- __demos__ >
 # Demos
 [DemoFluidDistort01Kt](src/demo/kotlin/DemoFluidDistort01Kt.kt
diff --git a/orx-fx/build.gradle.kts b/orx-fx/build.gradle.kts
index 6a966af9..25c70d8a 100644
--- a/orx-fx/build.gradle.kts
+++ b/orx-fx/build.gradle.kts
@@ -23,6 +23,8 @@ kotlin {
                     dependencies {
                         implementation(project(":orx-color"))
                         implementation(project(":orx-camera"))
+                        implementation(project(":orx-fx"))
+
                         implementation(libs.openrndr.application)
                         implementation(libs.openrndr.extensions)
                         runtimeOnly(libs.openrndr.gl3.core)
diff --git a/orx-fx/src/commonMain/kotlin/Post.kt b/orx-fx/src/commonMain/kotlin/Post.kt
new file mode 100644
index 00000000..6be90250
--- /dev/null
+++ b/orx-fx/src/commonMain/kotlin/Post.kt
@@ -0,0 +1,108 @@
+package org.openrndr.extra.fx
+
+import org.openrndr.Extension
+import org.openrndr.Program
+import org.openrndr.draw.*
+
+class Post : Extension {
+    override var enabled = true
+
+    private var inputTarget: RenderTarget? = null
+    private var resolved: ColorBuffer? = null
+
+    /**
+     * The color type to use for the intermediate color buffers
+     */
+    var intermediateType = ColorType.UINT8
+
+    /**
+     * The color type to use for the output color buffer
+     */
+    var outputType = ColorType.UINT8
+
+    /**
+     * The color type to use for the input buffer
+     */
+    var inputType = ColorType.UINT8
+
+    private var output: ColorBuffer? = null
+    private var postFunction = { input: ColorBuffer, output: ColorBuffer -> input.copyTo(output) }
+
+    inner class IntermediateBuffers {
+        internal val buffers = mutableMapOf<Int, ColorBuffer>()
+        operator fun get(index: Int) : ColorBuffer {
+            return buffers.getOrPut(index) {
+                colorBuffer(output!!.width, output!!.height, output!!.contentScale, type = intermediateType)
+            }
+        }
+    }
+
+    /**
+     * Intermediate buffer pool, provides automatically allocated color buffers
+     */
+    val intermediate = IntermediateBuffers()
+
+    /**
+     * Set the post function
+     * @param function the post function
+     */
+    fun post(function: (input: ColorBuffer, output: ColorBuffer) -> Unit) {
+        postFunction = function
+    }
+
+    override fun beforeDraw(drawer: Drawer, program: Program) {
+        val art = RenderTarget.active
+        val lit = inputTarget
+        if (lit != null) {
+            // in case the attributes of the existing buffers no longer match those of the active render target
+            if (lit.width != art.width || lit.height != art.height || lit.contentScale != art.contentScale || lit.multisample != art.multisample) {
+                lit.colorBuffer(0).destroy()
+                lit.detachColorAttachments()
+                lit.destroy()
+                inputTarget = null
+
+                resolved?.destroy()
+                resolved = null
+
+                output?.destroy()
+                output = null
+
+                for (buffer in intermediate.buffers.values) {
+                    buffer.destroy()
+                }
+                intermediate.buffers.clear()
+            }
+        }
+        if (inputTarget == null) {
+            // create new targets and buffers
+            inputTarget = renderTarget(art.width, art.height, art.contentScale, multisample = art.multisample) {
+                colorBuffer(type = inputType)
+            }
+            if (art.multisample != BufferMultisample.Disabled) {
+                resolved = colorBuffer(art.width, art.height, art.contentScale)
+            }
+            output = colorBuffer(art.width, art.height, art.contentScale, type = outputType)
+        }
+        // bind input target, the next extensions will draw into it
+        inputTarget!!.bind()
+    }
+
+    override fun afterDraw(drawer: Drawer, program: Program) {
+        inputTarget!!.unbind()
+
+        if (resolved != null) {
+            inputTarget!!.colorBuffer(0).copyTo(resolved!!)
+        }
+
+        val postInput = resolved ?: inputTarget!!.colorBuffer(0)
+
+        // invoke the user provided post-processing function
+        postFunction(postInput, output!!)
+
+        // visualize the results
+        drawer.isolated {
+            drawer.defaults()
+            drawer.image(output!!)
+        }
+    }
+}
\ No newline at end of file
diff --git a/orx-fx/src/demo/kotlin/DemoPost01.kt b/orx-fx/src/demo/kotlin/DemoPost01.kt
new file mode 100644
index 00000000..f6157802
--- /dev/null
+++ b/orx-fx/src/demo/kotlin/DemoPost01.kt
@@ -0,0 +1,27 @@
+import org.openrndr.WindowMultisample
+import org.openrndr.application
+import org.openrndr.extra.fx.Post
+import org.openrndr.extra.fx.blend.Add
+import org.openrndr.extra.fx.blur.ApproximateGaussianBlur
+
+fun main() = application {
+    configure {
+        windowResizable = true
+    }
+    program {
+        extend(Post()) {
+            val blur = ApproximateGaussianBlur()
+            val add = Add()
+            post { input, output ->
+                blur.window = 50
+                blur.sigma = 50.0
+                blur.apply(input, intermediate[0])
+                add.apply(arrayOf(input, intermediate[0]), output)
+            }
+        }
+        extend {
+            drawer.circle(width / 2.0, height / 2.0, 100.0)
+        }
+    }
+}
+