camera 拉伸填坑

AndroidTv Camera填坑记

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目标机型

• 当贝智慧盒子Z1 Pro
  https://item.jd.com/100018294794.html?cu=true&utm_source=api.shop.xuelg.com&utm_medium=jingfen&utm_campaign=t_2011134073_&utm_term=6695149d20d9457497e97b1a13a5e4c4

坑

camera预览图像拉伸

• 为了进一步处理问题，阅读了【数字图像与视频处理】，算是一些饭前甜点

其中关键核心是YUV 格式和RGB转换
具体参考了：https://github.com/gordinmitya/yuv2buf

简述一下：YUV即通过Y、U和V三个分量表示颜色空间，其中Y表示亮度，U和V表示色度。

YUV_420_888 是一个通用格式，分I420, YV12, NV21, and NV12这几种

具体参考如下：

image.png

• 操刀

class AutoFitSurfaceView @JvmOverloads constructor(
        context: Context,
        attrs: AttributeSet? = null,
        defStyle: Int = 0
) : SurfaceView(context, attrs, defStyle) {

    private var aspectRatio = 0f

    /**
     * Sets the aspect ratio for this view. The size of the view will be
     * measured based on the ratio calculated from the parameters.
     *
     * @param width  Camera resolution horizontal size
     * @param height Camera resolution vertical size
     */
    fun setAspectRatio(width: Int, height: Int) {
        require(width > 0 && height > 0) { "Size cannot be negative" }
        aspectRatio = width.toFloat() / height.toFloat()
        holder.setFixedSize(width, height)
        requestLayout()
    }

    override fun onMeasure(widthMeasureSpec: Int, heightMeasureSpec: Int) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec)
        val width = MeasureSpec.getSize(widthMeasureSpec)
        val height = MeasureSpec.getSize(heightMeasureSpec)
        if (aspectRatio == 0f) {
            setMeasuredDimension(width, height)
        } else {

            // Performs center-crop transformation of the camera frames
            val newWidth: Int
            val newHeight: Int
            val actualRatio = if (width > height) aspectRatio else 1f / aspectRatio
            if (width < height * actualRatio) {
                newHeight = height
                newWidth = (height * actualRatio).roundToInt()
            } else {
                newWidth = width
                newHeight = (width / actualRatio).roundToInt()
            }

            Log.d(TAG, "Measured dimensions set: $newWidth x $newHeight")
            setMeasuredDimension(newWidth, newHeight)
        }
    }

    companion object {
        private val TAG = AutoFitSurfaceView::class.java.simpleName
    }
}

• 计算预览大小

//        AutoFitSurfaceView xml配置

       AutoFitSurfaceView.addCallback(object : SurfaceHolder.Callback {
            override fun surfaceDestroyed(holder: SurfaceHolder) = Unit

            override fun surfaceChanged(
                    holder: SurfaceHolder,
                    format: Int,
                    width: Int,
                    height: Int) = Unit

            override fun surfaceCreated(holder: SurfaceHolder) {
                // Selects appropriate preview size and configures view finder
                val previewSize = getPreviewOutputSize(
                    AutoFitSurfaceView .display,
                    characteristics,
                    SurfaceHolder::class.java
                )
      
              AutoFitSurfaceView.setAspectRatio(
                    previewSize.width,
                    previewSize.height
                )

            }
        })

• 获取相机最大的预览尺寸 Returns the largest available PREVIEW size
  https://d.android.com/reference/android/hardware/camera2/CameraDevice
  https://developer.android.com/reference/android/hardware/camera2/params/StreamConfigurationMap

fun <T>getPreviewOutputSize(
        display: Display,
        characteristics: CameraCharacteristics,
        targetClass: Class<T>,
        format: Int? = null
): Size {

    // Find which is smaller: screen or 1080p
    val screenSize = getDisplaySmartSize(display)
    val hdScreen = screenSize.long >= SIZE_1080P.long || screenSize.short >= SIZE_1080P.short
    val maxSize = if (hdScreen) SIZE_1080P else screenSize

    // If image format is provided, use it to determine supported sizes; else use target class
    val config = characteristics.get(
            CameraCharacteristics.SCALER_STREAM_CONFIGURATION_MAP)!!
    if (format == null)
        assert(StreamConfigurationMap.isOutputSupportedFor(targetClass))
    else
        assert(config.isOutputSupportedFor(format))
    val allSizes = if (format == null)
        config.getOutputSizes(targetClass) else config.getOutputSizes(format)

    // Get available sizes and sort them by area from largest to smallest
    val validSizes = allSizes
            .sortedWith(compareBy { it.height * it.width })
            .map { SmartSize(it.width, it.height) }.reversed()

    // Then, get the largest output size that is smaller or equal than our max size
    return validSizes.first { it.long <= maxSize.long && it.short <= maxSize.short }.size
}

class SmartSize(width: Int, height: Int) {
    var size = Size(width, height)
    var long = max(size.width, size.height)
    var short = min(size.width, size.height)
    override fun toString() = "SmartSize(${long}x${short})"
}

val SIZE_1080P: SmartSize = SmartSize(1920, 1080)

fun getDisplaySmartSize(display: Display): SmartSize {
    val outPoint = Point()
    display.getRealSize(outPoint)
    return SmartSize(outPoint.x, outPoint.y)
}