Android：拍摄的照片比预览大 [英] Android: Taken photo is bigger than the preview

问题描述

我试图直接使用camera api捕获照片，但这是我的预览：

I'm trying to capture photos directly using the camera api, but this is the preview I got:

&这是调用 takePicture（）之后拍摄的图片，比预览本身大：

& this is the image taken after calling takePicture() which is bigger than the preview itself:

（注意：我裁剪了前面2张照片，以提高问题的可读性，并保持原样的宽度）

(note: I cropped the height of the previous 2 photos to enhance question readability, & kept the width as is)

我使用此实用程序方法选择最佳最佳预览大小开始相机预览之前：

I'm using this utility method to choose best optimal preview size before starting the camera preview:

public static Camera.Size getBestAspectPreviewSize(int displayOrientation,
                                                   int width,
                                                   int height,
                                                   Camera.Parameters parameters) {
    double targetRatio = (double) width / height;
    Camera.Size optimalSize = null;
    double minDiff = Double.MAX_VALUE;
    if (displayOrientation == 90 || displayOrientation == 270) {
        targetRatio = (double) height / width;
    }
    List<Camera.Size> sizes = parameters.getSupportedPreviewSizes();
    Collections.sort(sizes,
            Collections.reverseOrder(new SizeComparator()));
    for (Camera.Size size : sizes) {
        double ratio = (double) size.width / size.height;
        if (Math.abs(ratio - targetRatio) < minDiff) {
            optimalSize = size;
            minDiff = Math.abs(ratio - targetRatio);
        }
        if (minDiff < 0.0d) {
            break;
        }
    }
    return (optimalSize);
}

&这种方法选择合适的图片大小：

& this method to choose a suitable picture size:

public static Camera.Size getBiggestSafePictureSize(Camera.Parameters parameters) {
    Camera.Size result = null;
    long used = Runtime.getRuntime().totalMemory() - Runtime.getRuntime().freeMemory();
    long availableMemory = Runtime.getRuntime().maxMemory() - used;
    for (Camera.Size size : parameters.getSupportedPictureSizes()) {
        int newArea = size.width * size.height;
        long neededMemory = newArea * 4 * 4; // newArea * 4 Bytes/pixel * 4 needed copies of the bitmap (for safety :) )
        if (neededMemory > availableMemory)
            continue;
        if (result == null) {
            result = size;
        } else {
            int resultArea = result.width * result.height;
            if (newArea > resultArea) {
                result = size;
            }
        }
    }
    return (result);
}

&这是布局中的相机预览元素：

& this is the camera preview element in the layout:

<FrameLayout
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:id="@+id/cameraPreview"></FrameLayout>

&我正在官方文档中创建相机预览本身

& I'm following the official documentation for creating the camera preview itself

那么，如何强制相机预览显示准确的照片？

So, how to force the camera preview to show the exact photo that will be taken?

推荐答案

最后我发现：

根据 answer &我引用：

according to this answer & I quote:

虽然典型的相机是 4：3 宽高比，在5：3和16：9的比例，这似乎是通过实际扩展水平视野...

While the typical camera is a 4:3 aspect ratio, the preview may also be available in 5:3 and 16:9 ratios and this seems to be accomplished by actually extending the horizontal field of view...

我们需要找到一个预览大小图片尺寸（均为 4：3 宽高比），以便能够利用相机的全角度，因此我更改了我的代码：

So we need to find a preview size & a picture size, both with 4:3 aspect ratio to be able to utilize the full angle of the camera, so I changed my code like this:

public static Camera.Size determineBestPreviewSize(Camera.Parameters parameters) {
    List<Camera.Size> sizes = parameters.getSupportedPreviewSizes();
    return determineBestSize(sizes);
}

public static Camera.Size determineBestPictureSize(Camera.Parameters parameters) {
    List<Camera.Size> sizes = parameters.getSupportedPictureSizes();
    return determineBestSize(sizes);
}

protected static Camera.Size determineBestSize(List<Camera.Size> sizes) {
    Camera.Size bestSize = null;
    long used = Runtime.getRuntime().totalMemory() - Runtime.getRuntime().freeMemory();
    long availableMemory = Runtime.getRuntime().maxMemory() - used;
    for (Camera.Size currentSize : sizes) {
        int newArea = currentSize.width * currentSize.height;
        long neededMemory = newArea * 4 * 4; // newArea * 4 Bytes/pixel * 4 needed copies of the bitmap (for safety :) )
        boolean isDesiredRatio = (currentSize.width / 4) == (currentSize.height / 3);
        boolean isBetterSize = (bestSize == null || currentSize.width > bestSize.width);
        boolean isSafe = neededMemory < availableMemory;
        if (isDesiredRatio && isBetterSize && isSafe) {
            bestSize = currentSize;
        }
    }
    if (bestSize == null) {
        return sizes.get(0);
    }
    return bestSize;
}

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