Update

core/src/main/common/org/isoron/platform/gui/Canvas.kt

@@ -47,4 +47,6 @@ interface Canvas {
                 swipeAngle: Double)
     fun fillCircle(centerX: Double, centerY: Double, radius: Double)
     fun setTextAlign(align: TextAlign)
-}
+    fun toImage(): Image
+}
+

core/src/main/common/org/isoron/platform/gui/Image.kt

@@ -0,0 +1,64 @@
+/*
+ * Copyright (C) 2016-2019 Álinson Santos Xavier <isoron@gmail.com>
+ *
+ * This file is part of Loop Habit Tracker.
+ *
+ * Loop Habit Tracker is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by the
+ * Free Software Foundation, either version 3 of the License, or (at your
+ * option) any later version.
+ *
+ * Loop Habit Tracker is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package org.isoron.platform.gui
+
+import kotlin.math.*
+
+interface Image {
+    val width: Int
+    val height: Int
+
+    fun getPixel(x: Int, y: Int): Color
+    fun setPixel(x: Int, y: Int, color: Color)
+
+    suspend fun export(path: String)
+
+    fun diff(other: Image) {
+        if (width != other.width) error("Width must match")
+        if (height != other.height) error("Height must match")
+
+        for (x in 0 until width) {
+            for (y in 0 until height) {
+                val p1 = getPixel(x, y)
+                var l = 1.0
+                for (dx in -2..2) {
+                    if (x + dx < 0 || x + dx >= width) continue
+                    for (dy in -2..2) {
+                        if (y + dy < 0 || y + dy >= height) continue
+                        val p2 = other.getPixel(x + dx, y + dy)
+                        l = min(l, abs(p1.luminosity - p2.luminosity))
+                    }
+                }
+                setPixel(x, y, Color(l, l, l, 1.0))
+            }
+        }
+    }
+
+    val averageLuminosity: Double
+        get() {
+            var luminosity = 0.0
+            for (x in 0 until width) {
+                for (y in 0 until height) {
+                    luminosity += getPixel(x, y).luminosity
+                }
+            }
+            return luminosity / (width * height)
+        }
+}

core/src/main/common/org/isoron/platform/io/Files.kt

@@ -19,6 +19,8 @@
 
 package org.isoron.platform.io
 
+import org.isoron.platform.gui.*
+
 interface FileOpener {
     /**
      * Opens a file which was shipped bundled with the application, such as a
@@ -88,4 +90,9 @@ interface ResourceFile {
      * Returns true if the file exists.
      */
     suspend fun exists(): Boolean
+
+    /**
+     * Loads resource file as an image.
+     */
+    suspend fun toImage(): Image
 }

core/src/main/ios/org/isoron/platform/gui/IosCanvas.kt

@@ -28,8 +28,7 @@ val Color.uicolor: UIColor
 val Color.cgcolor: CGColorRef?
     get() = uicolor.CGColor
 
-class IosCanvas() : Canvas {
-    val ctx = UIGraphicsGetCurrentContext()
+class IosCanvas(val ctx: CGContextRef) : Canvas {
     var textColor = UIColor.blackColor
 
     override fun setColor(color: Color) {
@@ -79,4 +78,8 @@ class IosCanvas() : Canvas {
 
     override fun setTextAlign(align: TextAlign) {
     }
+
+    override fun toImage(): Image {
+        TODO()
+    }
 }

core/src/main/ios/org/isoron/platform/io/IosFiles.kt

@@ -21,6 +21,7 @@
 
 package org.isoron.platform.io
 
+import org.isoron.platform.gui.*
 import platform.Foundation.*
 
 class IosFileOpener : FileOpener {
@@ -54,6 +55,11 @@ class IosFile(val path: String) : UserFile, ResourceFile {
     }
 
     override suspend fun copyTo(dest: UserFile) {
-        NSFileManager.defaultManager.copyItemAtPath(path, (dest as IosFile).path, null)
+        val manager = NSFileManager.defaultManager
+        manager.copyItemAtPath(path, (dest as IosFile).path, null)
+    }
+
+    override suspend fun toImage(): Image {
+        TODO()
     }
 }

core/src/main/js/org/isoron/platform/gui/JsCanvas.kt

@@ -27,6 +27,7 @@ import kotlin.math.*
 class JsCanvas(val element: HTMLCanvasElement,
                val pixelScale: Double) : Canvas {
 
+
     val ctx = element.getContext("2d") as CanvasRenderingContext2D
     var fontSize = 12.0
     var fontFamily = "NotoRegular"
@@ -57,7 +58,7 @@ class JsCanvas(val element: HTMLCanvasElement,
         ctx.font = "${fontSize}px ${fontFamily}"
         ctx.textAlign = align
         ctx.textBaseline = CanvasTextBaseline.MIDDLE
-        ctx.fillText(text, toPixel(x), toPixel(y + fontSize * 0.05))
+        ctx.fillText(text, toPixel(x), toPixel(y + fontSize * 0.025))
     }
 
     override fun fillRect(x: Double, y: Double, width: Double, height: Double) {
@@ -83,7 +84,7 @@ class JsCanvas(val element: HTMLCanvasElement,
     }
 
     override fun setFont(font: Font) {
-        fontFamily = when(font) {
+        fontFamily = when (font) {
             Font.REGULAR -> "NotoRegular"
             Font.BOLD -> "NotoBold"
             Font.FONT_AWESOME -> "FontAwesome"
@@ -125,21 +126,18 @@ class JsCanvas(val element: HTMLCanvasElement,
     }
 
     override fun setTextAlign(align: TextAlign) {
-        this.align = when(align) {
+        this.align = when (align) {
             TextAlign.LEFT -> CanvasTextAlign.LEFT
             TextAlign.CENTER -> CanvasTextAlign.CENTER
             TextAlign.RIGHT -> CanvasTextAlign.RIGHT
         }
     }
 
-    suspend fun loadImage(src: String) {
-        Promise<Int> { resolve, reject ->
-            val img = Image()
-            img.onload = {
-                ctx.drawImage(img, 0.0, 0.0)
-                resolve(0)
-            }
-            img.src = src
-        }.await()
+    override fun toImage(): Image {
+        return JsImage(this,
+                       ctx.getImageData(0.0,
+                                        0.0,
+                                        element.width.toDouble(),
+                                        element.height.toDouble()))
     }
 }

core/src/main/js/org/isoron/platform/gui/JsImage.kt

@@ -0,0 +1,72 @@
+/*
+ * Copyright (C) 2016-2019 Álinson Santos Xavier <isoron@gmail.com>
+ *
+ * This file is part of Loop Habit Tracker.
+ *
+ * Loop Habit Tracker is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by the
+ * Free Software Foundation, either version 3 of the License, or (at your
+ * option) any later version.
+ *
+ * Loop Habit Tracker is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package org.isoron.platform.gui
+
+import org.khronos.webgl.*
+import org.w3c.dom.*
+import kotlin.browser.*
+import kotlin.math.*
+
+class JsImage(val canvas: JsCanvas,
+              val imageData: ImageData) : Image {
+
+    override val width: Int
+        get() = imageData.width
+
+    override val height: Int
+        get() = imageData.height
+
+    val pixels = imageData.unsafeCast<Uint16Array>()
+
+    init {
+        console.log(width, height, imageData.data.length)
+    }
+
+    override suspend fun export(path: String) {
+        canvas.ctx.putImageData(imageData, 0.0, 0.0)
+        val container = document.createElement("div")
+        container.className = "export"
+        val title = document.createElement("div")
+        title.innerHTML = path
+        document.body?.appendChild(container)
+        container.appendChild(title)
+        container.appendChild(canvas.element)
+    }
+
+    override fun getPixel(x: Int, y: Int): Color {
+        val offset = 4 * (y * width + x)
+        return Color(imageData.data[offset + 0] / 255.0,
+                     imageData.data[offset + 1] / 255.0,
+                     imageData.data[offset + 2] / 255.0,
+                     imageData.data[offset + 3] / 255.0)
+    }
+
+    override fun setPixel(x: Int, y: Int, color: Color) {
+        val offset = 4 * (y * width + x)
+        inline fun map(x: Double): Byte {
+           return (x * 255).roundToInt().unsafeCast<Byte>()
+        }
+        imageData.data.set(offset + 0, map(color.red))
+        imageData.data.set(offset + 1, map(color.green))
+        imageData.data.set(offset + 2, map(color.blue))
+        imageData.data.set(offset + 3, map(color.alpha))
+    }
+
+}

core/src/main/js/org/isoron/platform/io/JsFiles.kt

@@ -20,7 +20,11 @@
 package org.isoron.platform.io
 
 import kotlinx.coroutines.*
+import org.isoron.platform.gui.*
+import org.isoron.platform.gui.Image
+import org.w3c.dom.*
 import org.w3c.xhr.*
+import kotlin.browser.*
 import kotlin.js.*
 
 class JsFileStorage {
@@ -142,4 +146,20 @@ class JsResourceFile(val filename: String) : ResourceFile {
         val fs = (dest as JsUserFile).fs
         fs.put(dest.filename, lines().joinToString("\n"))
     }
+
+    override suspend fun toImage(): Image {
+        return Promise<Image> { resolve, reject ->
+            val img = org.w3c.dom.Image()
+            img.onload = {
+                val canvas = JsCanvas(document.createElement("canvas") as HTMLCanvasElement, 1.0)
+                canvas.element.width = img.naturalWidth
+                canvas.element.height = img.naturalHeight
+                canvas.setColor(Color(0xffffff))
+                canvas.fillRect(0.0, 0.0, canvas.getWidth(), canvas.getHeight())
+                canvas.ctx.drawImage(img, 0.0, 0.0)
+                resolve(canvas.toImage())
+            }
+            img.src = "/assets/$filename"
+        }.await()
+    }
 }

core/src/main/jvm/org/isoron/platform/gui/JavaCanvas.kt

@@ -30,6 +30,9 @@ import kotlin.math.*
 
 class JavaCanvas(val image: BufferedImage,
                  val pixelScale: Double = 2.0) : Canvas {
+    override fun toImage(): Image {
+        return JavaImage(image)
+    }
 
     private val frc = FontRenderContext(null, true, true)
     private var fontSize = 12.0

core/src/main/jvm/org/isoron/platform/gui/JavaImage.kt

@@ -0,0 +1,48 @@
+/*
+ * Copyright (C) 2016-2019 Álinson Santos Xavier <isoron@gmail.com>
+ *
+ * This file is part of Loop Habit Tracker.
+ *
+ * Loop Habit Tracker is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by the
+ * Free Software Foundation, either version 3 of the License, or (at your
+ * option) any later version.
+ *
+ * Loop Habit Tracker is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package org.isoron.platform.gui
+
+import java.awt.image.*
+import java.io.*
+import javax.imageio.*
+
+class JavaImage(val bufferedImage: BufferedImage) : Image {
+    override fun setPixel(x: Int, y: Int, color: Color) {
+        bufferedImage.setRGB(x, y, java.awt.Color(color.red.toFloat(),
+                                                  color.green.toFloat(),
+                                                  color.blue.toFloat()).rgb)
+    }
+
+    override suspend fun export(path: String) {
+        val file = File(path)
+        file.parentFile.mkdirs()
+        ImageIO.write(bufferedImage, "png", file)
+    }
+
+    override val width: Int
+        get() = bufferedImage.width
+
+    override val height: Int
+        get() = bufferedImage.height
+
+    override fun getPixel(x: Int, y: Int): Color {
+        return Color(bufferedImage.getRGB(x, y))
+    }
+}

core/src/main/jvm/org/isoron/platform/io/JavaFiles.kt

@@ -19,8 +19,10 @@
 
 package org.isoron.platform.io
 
+import org.isoron.platform.gui.*
 import java.io.*
 import java.nio.file.*
+import javax.imageio.*
 
 class JavaResourceFile(val path: String) : ResourceFile {
     private val javaPath: Path
@@ -49,6 +51,10 @@ class JavaResourceFile(val path: String) : ResourceFile {
     fun stream(): InputStream {
         return Files.newInputStream(javaPath)
     }
+
+    override suspend fun toImage(): Image {
+        return JavaImage(ImageIO.read(stream()))
+    }
 }
 
 class JavaUserFile(val path: Path) : UserFile {