From 47d2c94df5db8e725628aca9b0ea3c69145e1311 Mon Sep 17 00:00:00 2001
From: Edwin Jakobs <edwin@rndr.studio>
Date: Thu, 17 Jan 2019 19:39:31 +0100
Subject: [PATCH] Add FastIntegralImage

---
 .../src/main/kotlin/FastIntegralImage.kt      | 77 +++++++++++++++++++
 .../resources/shaders/gl3/integral-image.frag | 26 +++++++
 2 files changed, 103 insertions(+)
 create mode 100644 orx-integral-image/src/main/kotlin/FastIntegralImage.kt
 create mode 100644 orx-integral-image/src/main/resources/shaders/gl3/integral-image.frag

diff --git a/orx-integral-image/src/main/kotlin/FastIntegralImage.kt b/orx-integral-image/src/main/kotlin/FastIntegralImage.kt
new file mode 100644
index 00000000..feaad8f4
--- /dev/null
+++ b/orx-integral-image/src/main/kotlin/FastIntegralImage.kt
@@ -0,0 +1,77 @@
+package org.openrndr.extra.integralimage
+
+import org.openrndr.draw.*
+import org.openrndr.filter.blend.passthrough
+import org.openrndr.math.Vector2
+import org.openrndr.resourceUrl
+
+
+class FastIntegralImageFilter : Filter(filterShaderFromUrl(resourceUrl(
+        "/shaders/gl3/integral-image.frag"
+))) {
+    var passIndex: Int by parameters
+    var passDirection: Vector2 by parameters
+    var sampleCount: Int by parameters
+    var sampleCountBase: Int by parameters
+}
+
+class FastIntegralImage : Filter(filterShaderFromUrl(resourceUrl(
+        "/shaders/gl3/integral-image.frag"
+))) {
+
+    var intermediate: ColorBuffer? = null
+    val filter = FastIntegralImageFilter()
+
+    private fun sampleCounts(size:Int, sampleCountBase:Int) : List<Int> {
+        var remainder = size
+        val sampleCounts = mutableListOf<Int>()
+        while (remainder > 0) {
+            sampleCounts += if (remainder >= sampleCountBase) {
+                sampleCountBase
+            } else {
+                remainder
+            }
+            remainder /= sampleCountBase
+        }
+        return sampleCounts
+    }
+
+    override fun apply(source: Array<ColorBuffer>, target: Array<ColorBuffer>) {
+
+        val sampleCountBase = 16
+        val xSampleCounts = sampleCounts(source[0].width, sampleCountBase)
+        val ySampleCounts = sampleCounts(source[0].height, sampleCountBase)
+
+        val li = intermediate
+        if (li == null || (li.width != source[0].width || li.height != source[0].height)) {
+            intermediate?.destroy()
+            intermediate = colorBuffer(source[0].width, source[0].height, 1.0, ColorFormat.RGBa, ColorType.FLOAT32)
+        }
+
+        val targets = arrayOf(target, arrayOf(intermediate!!))
+
+        var targetIndex = 0
+
+        filter.sampleCountBase = sampleCountBase
+
+        filter.passDirection = Vector2.UNIT_X
+        for (pass in 0 until xSampleCounts.size) {
+            filter.sampleCount = xSampleCounts[pass]
+            filter.passIndex = pass
+            filter.apply( if (pass == 0) source else targets[targetIndex%2], targets[(targetIndex+1)%2])
+            targetIndex++
+        }
+
+        filter.passDirection = Vector2.UNIT_Y
+        for (pass in 0 until ySampleCounts.size) {
+            filter.sampleCount = ySampleCounts[pass]
+            filter.passIndex = pass
+            filter.apply( targets[targetIndex%2], targets[(targetIndex+1)%2])
+            targetIndex++
+        }
+
+        if (targetIndex%2 == 1) {
+            passthrough.apply(targets[1], targets[0])
+        }
+    }
+}
\ No newline at end of file
diff --git a/orx-integral-image/src/main/resources/shaders/gl3/integral-image.frag b/orx-integral-image/src/main/resources/shaders/gl3/integral-image.frag
new file mode 100644
index 00000000..0b304920
--- /dev/null
+++ b/orx-integral-image/src/main/resources/shaders/gl3/integral-image.frag
@@ -0,0 +1,26 @@
+#version 330 core
+
+uniform sampler2D tex0;
+in vec2 v_texCoord0;
+out vec4 o_color;
+
+uniform int passIndex;
+uniform int sampleCount;
+uniform int sampleCountBase;
+uniform vec2 passDirection;
+
+
+void main() {
+    vec2 passOffset = vec2(pow(sampleCountBase, passIndex)) * (1.0/textureSize(tex0, 0)) * passDirection;
+
+    vec2 uv0 = v_texCoord0;
+    vec4 result = vec4(0.0);
+    for (int i = 0; i < sampleCount; ++i) {
+        vec2 readUV = v_texCoord0 - vec2(i *passOffset);
+        float factor = step(0.0, readUV.x) * step(0.0, readUV.y);
+        result += factor * texture(tex0, readUV);
+    }
+
+    o_color = result;
+
+}
\ No newline at end of file