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Camera: Improve documentation for android.control.zoomRatio

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To better document how android.control.zoomRatio works, add examples to
illustrate its relationship with scalerCropRegion.

Test: Build and read docs
Bug: 144780745
Change-Id: Iab0e849b4d045fc1648fcf2ddc51d84c66249273
gugelfrei
Shuzhen Wang 4 years ago
parent 1939a00071
commit 878f9df9e6
1 changed files with 61 additions and 20 deletions
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81
camera/ndk/include/camera/NdkCameraMetadataTags.h
Unescape View File

@ -1895,27 +1895,66 @@ typedef enum acamera_metadata_tag {
* ACAMERA_SCALER_CROP_REGION can still be used to specify the horizontal or vertical
* crop to achieve aspect ratios different than the native camera sensor.</p>
* <p>By using this control, the application gains a simpler way to control zoom, which can
* be a combination of optical and digital zoom. More specifically, for a logical
* multi-camera with more than one focal length, using a floating point zoom ratio offers
* more zoom precision when a telephoto lens is used, as well as allowing zoom ratio of
* less than 1.0 to zoom out to a wide field of view.</p>
* <p>Note that the coordinate system of cropRegion, AE/AWB/AF regions, and faces now changes
* to the effective after-zoom field-of-view represented by rectangle of (0, 0,
* activeArrayWidth, activeArrayHeight).</p>
* <p>For example, if ACAMERA_SENSOR_INFO_ACTIVE_ARRAY_SIZE is 4032*3024, and the preview stream
* is configured to the same 4:3 aspect ratio, the application can achieve 2.0x zoom in
* one of two ways:</p>
* <ul>
* <li>zoomRatio = 2.0, scaler.cropRegion = (0, 0, 4032, 3024)</li>
* <li>zoomRatio = 1.0 (default), scaler.cropRegion = (1008, 756, 3024, 2268)</li>
* be a combination of optical and digital zoom. For example, a multi-camera system may
* contain more than one lens with different focal lengths, and the user can use optical
* zoom by switching between lenses. Using zoomRatio has benefits in the scenarios below:
* <em> Zooming in from a wide-angle lens to a telephoto lens: A floating-point ratio provides
* better precision compared to an integer value of ACAMERA_SCALER_CROP_REGION.
* </em> Zooming out from a wide lens to an ultrawide lens: zoomRatio supports zoom-out whereas
* ACAMERA_SCALER_CROP_REGION doesn't.</p>
* <p>To illustrate, here are several scenarios of different zoom ratios, crop regions,
* and output streams, for a hypothetical camera device with an active array of size
* <code>(2000,1500)</code>.</p>
* <ul>
* <li>Camera Configuration:<ul>
* <li>Active array size: <code>2000x1500</code> (3 MP, 4:3 aspect ratio)</li>
* <li>Output stream #1: <code>640x480</code> (VGA, 4:3 aspect ratio)</li>
* <li>Output stream #2: <code>1280x720</code> (720p, 16:9 aspect ratio)</li>
* </ul>
* </li>
* <li>Case #1: 4:3 crop region with 2.0x zoom ratio<ul>
* <li>Zoomed field of view: 1/4 of original field of view</li>
* <li>Crop region: <code>Rect(0, 0, 2000, 1500) // (left, top, right, bottom)</code> (post zoom)</li>
* </ul>
* </li>
* <li><img alt="4:3 aspect ratio crop diagram" src="../images/camera2/metadata/android.control.zoomRatio/zoom-ratio-2-crop-43.png" /><ul>
* <li><code>640x480</code> stream source area: <code>(0, 0, 2000, 1500)</code> (equal to crop region)</li>
* <li><code>1280x720</code> stream source area: <code>(0, 187, 2000, 1312)</code> (letterboxed)</li>
* </ul>
* <p>If the application intends to set aeRegions to be top-left quarter of the preview
* field-of-view, the ACAMERA_CONTROL_AE_REGIONS should be set to (0, 0, 2016, 1512) with
* </li>
* <li>Case #2: 16:9 crop region with 2.0x zoom.<ul>
* <li>Zoomed field of view: 1/4 of original field of view</li>
* <li>Crop region: <code>Rect(0, 187, 2000, 1312)</code></li>
* <li><img alt="16:9 aspect ratio crop diagram" src="../images/camera2/metadata/android.control.zoomRatio/zoom-ratio-2-crop-169.png" /></li>
* <li><code>640x480</code> stream source area: <code>(250, 187, 1750, 1312)</code> (pillarboxed)</li>
* <li><code>1280x720</code> stream source area: <code>(0, 187, 2000, 1312)</code> (equal to crop region)</li>
* </ul>
* </li>
* <li>Case #3: 1:1 crop region with 0.5x zoom out to ultrawide lens.<ul>
* <li>Zoomed field of view: 4x of original field of view (switched from wide lens to ultrawide lens)</li>
* <li>Crop region: <code>Rect(250, 0, 1750, 1500)</code></li>
* <li><img alt="1:1 aspect ratio crop diagram" src="../images/camera2/metadata/android.control.zoomRatio/zoom-ratio-0.5-crop-11.png" /></li>
* <li><code>640x480</code> stream source area: <code>(250, 187, 1750, 1312)</code> (letterboxed)</li>
* <li><code>1280x720</code> stream source area: <code>(250, 328, 1750, 1172)</code> (letterboxed)</li>
* </ul>
* </li>
* </ul>
* <p>As seen from the graphs above, the coordinate system of cropRegion now changes to the
* effective after-zoom field-of-view, and is represented by the rectangle of (0, 0,
* activeArrayWith, activeArrayHeight). The same applies to AE/AWB/AF regions, and faces.
* This coordinate system change isn't applicable to RAW capture and its related
* metadata such as intrinsicCalibration and lensShadingMap.</p>
* <p>Using the same hypothetical example above, and assuming output stream #1 (640x480) is
* the viewfinder stream, the application can achieve 2.0x zoom in one of two ways:</p>
* <ul>
* <li>zoomRatio = 2.0, scaler.cropRegion = (0, 0, 2000, 1500)</li>
* <li>zoomRatio = 1.0 (default), scaler.cropRegion = (500, 375, 1500, 1125)</li>
* </ul>
* <p>If the application intends to set aeRegions to be top-left quarter of the viewfinder
* field-of-view, the ACAMERA_CONTROL_AE_REGIONS should be set to (0, 0, 1000, 750) with
* zoomRatio set to 2.0. Alternatively, the application can set aeRegions to the equivalent
* region of (1008, 756, 2016, 1512) for zoomRatio of 1.0. If the application doesn't
* region of (500, 375, 1000, 750) for zoomRatio of 1.0. If the application doesn't
* explicitly set ACAMERA_CONTROL_ZOOM_RATIO, its value defaults to 1.0.</p>
* <p>This coordinate system change isn't applicable to RAW capture and its related metadata
* such as intrinsicCalibration and lensShadingMap.</p>
* <p>One limitation of controlling zoom using zoomRatio is that the ACAMERA_SCALER_CROP_REGION
* must only be used for letterboxing or pillarboxing of the sensor active array, and no
* FREEFORM cropping can be used with ACAMERA_CONTROL_ZOOM_RATIO other than 1.0.</p>
@ -1923,7 +1962,6 @@ typedef enum acamera_metadata_tag {
* @see ACAMERA_CONTROL_AE_REGIONS
* @see ACAMERA_CONTROL_ZOOM_RATIO
* @see ACAMERA_SCALER_CROP_REGION
* @see ACAMERA_SENSOR_INFO_ACTIVE_ARRAY_SIZE
*/
ACAMERA_CONTROL_ZOOM_RATIO = // float
ACAMERA_CONTROL_START + 47,
@ -2395,8 +2433,11 @@ typedef enum acamera_metadata_tag {
* frames before the lens can change to the requested focal length.
* While the focal length is still changing, ACAMERA_LENS_STATE will
* be set to MOVING.</p>
* <p>Optical zoom will not be supported on most devices.</p>
* <p>Optical zoom via this control will not be supported on most devices. Starting from API
* level 30, the camera device may combine optical and digital zoom through the
* ACAMERA_CONTROL_ZOOM_RATIO control.</p>
*
* @see ACAMERA_CONTROL_ZOOM_RATIO
* @see ACAMERA_LENS_APERTURE
* @see ACAMERA_LENS_FOCUS_DISTANCE
* @see ACAMERA_LENS_STATE

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