android/src/com/android/tools/idea/rendering/GutterIconCache.java

/*
 * Copyright (C) 2013 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.android.tools.idea.rendering;

import com.google.common.collect.Maps;
import com.intellij.openapi.diagnostic.Logger;
import com.intellij.ui.Gray;
import com.intellij.util.RetinaImage;
import com.intellij.util.ui.UIUtil;
import icons.AndroidIcons;
import org.jetbrains.annotations.NotNull;
import org.jetbrains.annotations.Nullable;

import javax.imageio.ImageIO;
import javax.swing.*;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.util.Map;

public class GutterIconCache {
  private static final Logger LOG = Logger.getInstance(GutterIconCache.class);
  private static final int MAX_WIDTH = 16;
  private static final int MAX_HEIGHT = 16;
  private static final Icon NONE = AndroidIcons.Android; // placeholder

  private static final GutterIconCache ourInstance = new GutterIconCache();
  // TODO: Timestamps?
  private Map<String,Icon> myThumbnailCache = Maps.newHashMap();
  private boolean myRetina;
  private static boolean ourRetinaEnabled = true;

  public GutterIconCache() {
  }

  @NotNull
  public static GutterIconCache getInstance() {
    return ourInstance;
  }

  @Nullable
  public Icon getIcon(@NotNull String path) {
    boolean isRetina = UIUtil.isRetina();
    if (myRetina != isRetina) {
      myRetina = isRetina;
      myThumbnailCache.clear();
    }
    Icon myIcon = myThumbnailCache.get(path);
    if (myIcon == null) {
      myIcon = createIcon(path);

      if (myIcon == null) {
        myIcon = NONE;
      }

      myThumbnailCache.put(path, myIcon);
    }

    return myIcon != NONE ? myIcon : null;
  }

  @Nullable
  private static Icon createIcon(String path) {
    try {
      BufferedImage image = ImageIO.read(new File(path));
      if (image != null) {
        int imageWidth = image.getWidth();
        int imageHeight = image.getHeight();
        if (ourRetinaEnabled && UIUtil.isRetina()) {
          BufferedImage scaled = image;
          if (imageWidth > 2 * MAX_WIDTH || imageHeight > 2 * MAX_HEIGHT) {
            double scale = 2 * Math.min(MAX_WIDTH / (double)imageWidth, MAX_HEIGHT / (double)imageHeight);
            scaled = ImageUtils.scale(image, scale, scale);
          }

          // The Retina image uses a scale of 2, and the RetinaImage class creates an
          // image of size w/scale, h/scale. If the width or height is less than the scale,
          // this rounds to width or height 0, which will cause exceptions to be thrown.
          // Don't attempt to create a Retina image for images like that. See issue 65676.
          final int scale = 2;
          if (scaled.getWidth() >= scale && scaled.getHeight() >= scale) {
            try {
              @SuppressWarnings("ConstantConditions")
              Image hdpiImage = RetinaImage.createFrom(scaled, scale, null);
              return new RetinaImageIcon(hdpiImage);
            } catch (Throwable t) {
              // Can't always create Retina images (see issue 65609); fall through to non-Retina code path
              ourRetinaEnabled = false;
            }
          }
        }

        if (imageWidth > MAX_WIDTH || imageHeight > MAX_HEIGHT) {
          double scale = Math.min(MAX_WIDTH / (double)imageWidth, MAX_HEIGHT / (double)imageHeight);

          if (image.getType() == BufferedImage.TYPE_BYTE_INDEXED) {
            // Indexed images look terrible if they are scaled directly; instead, paint into an ARGB blank image
            BufferedImage bg = UIUtil.createImage(imageWidth, imageHeight, BufferedImage.TYPE_INT_ARGB);
            Graphics g = bg.getGraphics();
            //noinspection UseJBColor
            g.setColor(Gray.TRANSPARENT);
            g.fillRect(0, 0, bg.getWidth(), bg.getHeight());
            //noinspection ConstantConditions
            UIUtil.drawImage(g, image, 0, 0, null);
            g.dispose();
            image = bg;
          }

          image = ImageUtils.scale(image, scale, scale);
        }

        return new ImageIcon(image);
      }
    }
    catch (IOException e) {
      LOG.error(String.format("Could not read icon image %1$s", path), e);
    }

    return null;
  }

  private static class RetinaImageIcon extends ImageIcon {
    private RetinaImageIcon(Image image) {
      super(image, "");
    }

    @SuppressWarnings("ConstantConditions")
    @Override
    public synchronized void paintIcon(Component c, Graphics g, int x, int y) {
      UIUtil.drawImage(g, getImage(), x, y, null);
    }
  }
}