如何旋转相机预览以纵向模式拍摄风景照片？

Question

I see a lot of advice from people wanting to take portrait photos that tell them to rotate the camera by 90 degrees. However, no matter what I try the only thing that actually "rotates" is the image being taken by the camera, however it retains it's width and height proportions, so what happens is that the picture is only not distorted if the SurfaceView is narrow and tall.

What I'm trying to achieve is to take a 4x3 photo that is NOT warped in a 3x4 layout. It will be fairly narrow, I know, but the object is to rotate the Preview view -90degrees and yet preserve the normal aspect ratio of the Camera. As it stands, everything I've tried has resulted in the image being squished if I want to orient the photo across my portrait layout.

I'm starting to suspect that I'll need to apply a matrix to the Preview that will rotate it -90 degrees, but I'm not sure how to go about doing that, or if that's actually the right approach. Would love some advice.

Edit: Just to be clear here's the relevant excerpt from the javadocs: setPreviewSize() "If the display orientation is set to 0 or 180, preview size should be set to 480x320. If the display orientation is set to 90 or 270, preview size should be set to 320x480."

That totally fails to address the situation where you want to hold the device in portrait mode but have the camera preview appear in a small landscape window (which is what I'm trying to achieve).

TIA

Answer 1

If you're using a SurfaceView to display camera preview output, and you want to make sure your preview is not distorted, either in preview or in landscape, you have to make sure the aspect ratio of your SurfaceView matches the aspect ratio of the camera preview size. The SurfaceView will simply scale the preview to fit inside itself, so if it's 500x500 while your preview size is 640x480, preview will look stretched vertically.

The conceptually simplest approach is to simply manually set the SurfaceView's width and height, by updating the SurfaceView's layout to a fixed-size one with LayoutParams and setLayoutParams . The problem with this approach is that it can be brittle with different screen sizes, since you need to figure out what the sizes in pixels you want really are, and for straightforward across-device layout on Android, you really want to be thinking in dp instead of pixels. But for testing, you can just force your SurfaceView to have the width of the test device's screen, and height set by

surface height = preview height / preview width * surface width

A better approach would be to create a new class inherited from SurfaceView, which does the necessary aspect-ratio adjustments in the View's onMeasure method. Explaining that in detail is lengthy, but look over the custom components documentation on the Android developer's site for details. But roughly speaking, you need to set width/height values that always result in the same aspect ratio as the camera preview size you've configured.

Once you have the right-sized surfaceView, you do usually also need to rotate the camera preview output with setDisplayOrientation ; working out the orientation math can be confusing, so use the code sample provided at the documentation link above to work it out.

Basically, the world has one coordinate system, the camera sensor has another (fixed to the device), and the UI system has a third (fixed to your current orientation), and all three may change relative to each other. While the correct preview orientation does not depend on the position of the device relative to the world, the orientation of the pictures taken by the camera does (which is set by setRotation ).

Answer 2

My Suggestion is,

Don't try more on Layout in Android, it is very difficult to that stuff And iff you want to acheive, you must read the opensource code of Android and should change in that itself.

So, i suggest you to use Canvas(Import Graphics package) and make use of those classes.