Render themes: PNG scaling, fix #595

vtm/src/org/oscim/backend/CanvasAdapter.java

@@ -113,10 +113,25 @@ public abstract class CanvasAdapter {
      */
     protected abstract Bitmap decodeBitmapImpl(InputStream inputStream) throws IOException;
 
+    /**
+     * Create {@link Bitmap} from InputStream.
+     *
+     * @param inputStream the input stream
+     * @param width       requested width (0: no change)
+     * @param height      requested height (0: no change)
+     * @param percent     requested scale percent (100: no change)
+     * @return the bitmap
+     */
+    protected abstract Bitmap decodeBitmapImpl(InputStream inputStream, int width, int height, int percent) throws IOException;
+
     public static Bitmap decodeBitmap(InputStream inputStream) throws IOException {
         return g.decodeBitmapImpl(inputStream);
     }
 
+    public static Bitmap decodeBitmap(InputStream inputStream, int width, int height, int percent) throws IOException {
+        return g.decodeBitmapImpl(inputStream, width, height, percent);
+    }
+
     /**
      * Create SVG {@link Bitmap} from InputStream.
      *
@@ -182,7 +197,7 @@ public abstract class CanvasAdapter {
         if (src.toLowerCase(Locale.ENGLISH).endsWith(".svg"))
             bitmap = decodeSvgBitmap(inputStream, width, height, percent);
         else
-            bitmap = decodeBitmap(inputStream);
+            bitmap = decodeBitmap(inputStream, width, height, percent);
         inputStream.close();
         return bitmap;
     }

vtm/src/org/oscim/backend/canvas/Bitmap.java

@@ -1,6 +1,7 @@
 /*
  * Copyright 2013 Hannes Janetzek
  * Copyright 2016 Longri
+ * Copyright 2018 devemux86
  *
  * This file is part of the OpenScienceMap project (http://www.opensciencemap.org).
  *
@@ -65,4 +66,6 @@ public interface Bitmap {
     boolean isValid();
 
     byte[] getPngEncodedData();
+
+    void scaleTo(int width, int height);
 }

vtm/src/org/oscim/utils/GraphicUtils.java

@@ -0,0 +1,63 @@
+/*
+ * Copyright 2018 devemux86
+ *
+ * This program is free software: you can redistribute it and/or modify it under the
+ * terms of the GNU Lesser General Public License as published by the Free Software
+ * Foundation, either version 3 of the License, or (at your option) any later version.
+ *
+ * This program 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 Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License along with
+ * this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+package org.oscim.utils;
+
+/**
+ * Utility class for graphics operations.
+ */
+public final class GraphicUtils {
+
+    /**
+     * Given the original image size, as well as width, height, percent parameters,
+     * can compute the final image size.
+     *
+     * @param picWidth    original image width
+     * @param picHeight   original image height
+     * @param scaleFactor scale factor to screen DPI
+     * @param width       requested width (0: no change)
+     * @param height      requested height (0: no change)
+     * @param percent     requested scale percent (100: no change)
+     */
+    public static float[] imageSize(float picWidth, float picHeight, float scaleFactor, int width, int height, int percent) {
+        float bitmapWidth = picWidth * scaleFactor;
+        float bitmapHeight = picHeight * scaleFactor;
+
+        float aspectRatio = picWidth / picHeight;
+
+        if (width != 0 && height != 0) {
+            // both width and height set, override any other setting
+            bitmapWidth = width;
+            bitmapHeight = height;
+        } else if (width == 0 && height != 0) {
+            // only width set, calculate from aspect ratio
+            bitmapWidth = height * aspectRatio;
+            bitmapHeight = height;
+        } else if (width != 0 && height == 0) {
+            // only height set, calculate from aspect ratio
+            bitmapHeight = width / aspectRatio;
+            bitmapWidth = width;
+        }
+
+        if (percent != 100) {
+            bitmapWidth *= percent / 100f;
+            bitmapHeight *= percent / 100f;
+        }
+
+        return new float[]{bitmapWidth, bitmapHeight};
+    }
+
+    private GraphicUtils() {
+    }
+}