2 * Copyright (C) 2008 Google Inc.
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
8 * http://www.apache.org/licenses/LICENSE-2.0
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
17 package com.google.zxing.client.android;
19 import android.content.Context;
20 import android.graphics.Bitmap;
21 import android.graphics.Canvas;
22 import android.graphics.Point;
23 import android.graphics.Rect;
24 import android.hardware.CameraDevice;
25 import android.util.Log;
26 import android.view.Display;
27 import android.view.WindowManager;
28 import com.google.zxing.ResultPoint;
31 * This object wraps the CameraDevice and expects to be the only one talking to it. The
32 * implementation encapsulates the steps needed to take preview-sized images and well as high
35 * @author dswitkin@google.com (Daniel Switkin)
37 final class CameraManager {
39 private static final String TAG = "CameraManager";
41 private final Context context;
42 private Point cameraResolution;
43 private Point stillResolution;
44 private Point previewResolution;
45 private int stillMultiplier;
46 private Point screenResolution;
47 private Rect framingRect;
48 private Bitmap bitmap;
49 private CameraDevice camera;
50 private final CameraDevice.CaptureParams params;
51 private boolean previewMode;
52 private boolean usePreviewForDecode;
54 CameraManager(Context context) {
55 this.context = context;
56 getScreenResolution();
57 calculateStillResolution();
58 calculatePreviewResolution();
60 usePreviewForDecode = true;
61 setUsePreviewForDecode(false);
64 params = new CameraDevice.CaptureParams();
67 public void openDriver() {
69 camera = CameraDevice.open();
70 // If we're reopening the camera, we need to reset the capture params.
76 public void closeDriver() {
83 public void capturePreview(Canvas canvas) {
85 camera.capture(canvas);
88 public Bitmap captureStill() {
89 setPreviewMode(usePreviewForDecode);
90 Canvas canvas = new Canvas(bitmap);
91 camera.capture(canvas);
96 * This method exists to help us evaluate how to best set up and use the camera.
97 * @param usePreview Decode at preview resolution if true, else use still resolution.
99 public void setUsePreviewForDecode(boolean usePreview) {
100 if (usePreviewForDecode != usePreview) {
101 usePreviewForDecode = usePreview;
103 Log.v(TAG, "Creating bitmap at screen resolution: " + screenResolution.x + "," +
105 bitmap = Bitmap.createBitmap(screenResolution.x, screenResolution.y, false);
107 Log.v(TAG, "Creating bitmap at still resolution: " + stillResolution.x + "," +
109 bitmap = Bitmap.createBitmap(stillResolution.x, stillResolution.y, false);
115 * Calculates the framing rect which the UI should draw to show the user where to place the
116 * barcode. The actual captured image should be a bit larger than indicated because they might
117 * frame the shot too tightly. This target helps with alignment as well as forces the user to hold
118 * the device far enough away to ensure the image will be in focus.
120 * @return The rectangle to draw on screen in window coordinates.
122 public Rect getFramingRect() {
123 if (framingRect == null) {
124 int size = stillResolution.x * screenResolution.x / previewResolution.x;
125 int leftOffset = (screenResolution.x - size) / 2;
126 int topOffset = (screenResolution.y - size) / 2;
127 framingRect = new Rect(leftOffset, topOffset, leftOffset + size, topOffset + size);
128 Log.v(TAG, "Calculated framing rect: " + framingRect);
134 * Converts the result points from still resolution coordinates to screen coordinates.
136 * @param points The points returned by the Reader subclass through Result.getResultPoints().
137 * @return An array of Points scaled to the size of the framing rect and offset appropriately
138 * so they can be drawn in screen coordinates.
140 public Point[] convertResultPoints(ResultPoint[] points) {
141 Rect frame = getFramingRect();
142 int frameSize = frame.width();
143 int count = points.length;
144 Point[] output = new Point[count];
145 for (int x = 0; x < count; x++) {
146 output[x] = new Point();
147 if (usePreviewForDecode) {
148 output[x].x = (int) (points[x].getX() + 0.5f);
149 output[x].y = (int) (points[x].getY() + 0.5f);
151 output[x].x = frame.left + (int) (points[x].getX() * frameSize / stillResolution.x + 0.5f);
152 output[x].y = frame.top + (int) (points[x].getY() * frameSize / stillResolution.y + 0.5f);
159 * Images for the live preview are taken at low resolution in RGB. The final stills for the
160 * decoding step are taken in YUV, since we only need the luminance channel. Other code depends
161 * on the ability to call this method for free if the correct mode is already set.
163 * @param on Setting on true will engage preview mode, setting it false will request still mode.
165 private void setPreviewMode(boolean on) {
166 if (on != previewMode) {
168 params.type = 1; // preview
169 params.srcWidth = previewResolution.x;
170 params.srcHeight = previewResolution.y;
171 params.leftPixel = (cameraResolution.x - params.srcWidth) / 2;
172 params.topPixel = (cameraResolution.y - params.srcHeight) / 2;
173 params.outputWidth = screenResolution.x;
174 params.outputHeight = screenResolution.y;
175 params.dataFormat = 2; // RGB565
177 params.type = 0; // still
178 params.srcWidth = stillResolution.x * stillMultiplier;
179 params.srcHeight = stillResolution.y * stillMultiplier;
180 params.leftPixel = (cameraResolution.x - params.srcWidth) / 2;
181 params.topPixel = (cameraResolution.y - params.srcHeight) / 2;
182 params.outputWidth = stillResolution.x;
183 params.outputHeight = stillResolution.y;
184 params.dataFormat = 2; // RGB565
186 String captureType = on ? "preview" : "still";
187 Log.v(TAG, "Setting params for " + captureType + ": srcWidth " + params.srcWidth +
188 " srcHeight " + params.srcHeight + " leftPixel " + params.leftPixel + " topPixel " +
189 params.topPixel + " outputWidth " + params.outputWidth + " outputHeight " +
190 params.outputHeight);
191 camera.setCaptureParams(params);
197 * This method determines how to take the highest quality image (i.e. the one which has the best
198 * chance of being decoded) given the capabilities of the camera. It is a balancing act between
199 * having enough resolution to read UPCs and having few enough pixels to keep the QR Code
200 * processing fast. The result is the dimensions of the rectangle to capture from the center of
201 * the sensor, plus a stillMultiplier which indicates whether we'll ask the driver to downsample
202 * for us. This has the added benefit of keeping the memory footprint of the bitmap as small as
205 private void calculateStillResolution() {
206 cameraResolution = getMaximumCameraResolution();
207 int minDimension = (cameraResolution.x < cameraResolution.y) ? cameraResolution.x :
209 int diagonalResolution = (int) Math.sqrt(cameraResolution.x * cameraResolution.x +
210 cameraResolution.y * cameraResolution.y);
211 float diagonalFov = getFieldOfView();
213 // Determine the field of view in the smaller dimension, then calculate how large an object
214 // would be at the minimum focus distance.
215 float fov = diagonalFov * minDimension / diagonalResolution;
216 double objectSize = Math.tan(Math.toRadians(fov / 2.0)) * getMinimumFocusDistance() * 2;
218 // Let's assume the largest barcode we might photograph at this distance is 3 inches across. By
219 // cropping to this size, we can avoid processing surrounding pixels, which helps with speed and
221 // TODO(dswitkin): Handle a device with a great macro mode where objectSize < 4 inches.
222 double crop = 3.0 / objectSize;
223 int nativeResolution = (int) (minDimension * crop);
225 // The camera driver can only capture images which are a multiple of eight, so it's necessary to
227 nativeResolution = ((nativeResolution + 7) >> 3) << 3;
228 if (nativeResolution > minDimension) {
229 nativeResolution = minDimension;
232 // There's no point in capturing too much detail, so ask the driver to downsample. I haven't
233 // tried a non-integer multiple, but it seems unlikely to work.
234 double dpi = nativeResolution / objectSize;
237 stillMultiplier = (int) (dpi / 200 + 1);
239 stillResolution = new Point(nativeResolution, nativeResolution);
240 Log.v(TAG, "FOV " + fov + " objectSize " + objectSize + " crop " + crop + " dpi " + dpi +
241 " nativeResolution " + nativeResolution + " stillMultiplier " + stillMultiplier);
245 * The goal of the preview resolution is to show a little context around the framing rectangle
246 * which is the actual captured area in still mode.
248 private void calculatePreviewResolution() {
249 if (previewResolution == null) {
250 int previewHeight = (int) (stillResolution.x * stillMultiplier * 1.8f);
251 int previewWidth = previewHeight * screenResolution.x / screenResolution.y;
252 previewWidth = ((previewWidth + 7) >> 3) << 3;
253 if (previewWidth > cameraResolution.x) previewWidth = cameraResolution.x;
254 previewHeight = previewWidth * screenResolution.y / screenResolution.x;
255 previewResolution = new Point(previewWidth, previewHeight);
256 Log.v(TAG, "previewWidth " + previewWidth + " previewHeight " + previewHeight);
260 // FIXME(dswitkin): These three methods have temporary constants until the new Camera API can
261 // provide the real values for the current device.
262 // Temporary: the camera's maximum resolution in pixels.
263 private static Point getMaximumCameraResolution() {
264 return new Point(1280, 1024);
267 // Temporary: the diagonal field of view in degrees.
268 private static float getFieldOfView() {
272 // Temporary: the minimum focus distance in inches.
273 private static float getMinimumFocusDistance() {
277 private Point getScreenResolution() {
278 if (screenResolution == null) {
279 WindowManager manager = (WindowManager) context.getSystemService(Context.WINDOW_SERVICE);
280 Display display = manager.getDefaultDisplay();
281 screenResolution = new Point(display.getWidth(), display.getHeight());
283 return screenResolution;