You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
89 lines
3.6 KiB
89 lines
3.6 KiB
---
|
|
layout: page
|
|
title: "Preview Size"
|
|
subtitle: "Measuring behavior"
|
|
description: "Measuring behavior"
|
|
category: docs
|
|
order: 8
|
|
date: 2018-12-20 22:07:17
|
|
disqus: 1
|
|
---
|
|
|
|
`CameraView` has a smart measuring behavior that will let you do what you want with a few flags.
|
|
Measuring is controlled simply by `layout_width` and `layout_height` attributes, with this meaning:
|
|
|
|
|Value|Meaning|
|
|
|-----|-------|
|
|
|`WRAP_CONTENT`|CameraView will choose this dimension, in order to show the whole preview without cropping. The aspect ratio will be respected.|
|
|
|`MATCH_PARENT`|CameraView will fill this dimension. Part of the content *might* be cropped.
|
|
|Fixed values (e.g. `500dp`)|Same as `MATCH_PARENT`|
|
|
|
|
This means that your visible preview can be of any size, not just the presets.
|
|
Whatever you do, the preview will never be distorted - it can only be cropped
|
|
if needed.
|
|
|
|
## Examples
|
|
|
|
##### Center Inside
|
|
|
|
By setting both dimensions to `WRAP_CONTENT`, you can emulate a **center inside** behavior.
|
|
The view will try to fill the available space, but respecting the stream aspect ratio.
|
|
|
|
|
|
```xml
|
|
<com.otaliastudios.cameraview.CameraView
|
|
android:layout_width="wrap_content"
|
|
android:layout_height="wrap_content" />
|
|
```
|
|
|
|
This means that the whole preview is visible, and the image output matches what was visible
|
|
during the preview.
|
|
|
|
##### Center Crop
|
|
|
|
By setting both dimensions to `MATCH_PARENT` or fixed values, you can emulate a **center crop**
|
|
behavior. The camera view will fill the rect. If your dimensions don't match the aspect ratio
|
|
of the internal preview surface, the surface will be cropped to fill the view.
|
|
|
|
```xml
|
|
<com.otaliastudios.cameraview.CameraView
|
|
android:layout_width="match_parent"
|
|
android:layout_height="match_parent" />
|
|
```
|
|
|
|
This means that part of the preview might be hidden, and the output might contain parts of the scene
|
|
that were not visible during the capture, **unless it is taken as a snapshot, since snapshots account for cropping**.
|
|
|
|
|
|
## Advanced feature: Preview Stream Size Selection
|
|
|
|
**Only do this if you know what you are doing. This is typically not needed - prefer picture/video size selectors,
|
|
as they will drive the preview stream size selection and, eventually, the view size. If what you want is just
|
|
choose an aspect ratio, do so with [Capture Size](capture-size.html) selection.**
|
|
|
|
As said, `WRAP_CONTENT` adapts the view boundaries to the preview stream size. The preview stream size must be determined
|
|
based on the sizes that the device sensor & hardware actually support. This operation is done automatically
|
|
by the engine. The default selector will do the following:
|
|
|
|
- Constraint 1: match the picture/video output aspect ratio (so you get what you see)
|
|
- Constraint 2: match sizes a bit bigger than the View (so there is no upscaling)
|
|
- Try to match both, or just one, or fallback to the biggest available size
|
|
|
|
There are not so many reason why you would replace this, other than control the frame processor size
|
|
or, indirectly, the snapshot size. You can, however, hook into the process using `setPreviewStreamSize(SizeSelector)`:
|
|
|
|
```java
|
|
cameraView.setPreviewStreamSize(new SizeSelector() {
|
|
@Override
|
|
public List<Size> select(List<Size> source) {
|
|
// Receives a list of available sizes.
|
|
// Must return a list of acceptable sizes.
|
|
}
|
|
});
|
|
```
|
|
|
|
After the preview stream size is determined, if it has changed since list time, the `CameraView` will receive
|
|
another call to `onMeasure` so the `WRAP_CONTENT` magic can take place.
|
|
|
|
To understand how SizeSelectors work and the available utilities, please read the [Capture Size](capture-size.html) document.
|
|
|
|
|