MTK Camera2 预览图成像质量差（马赛克）

MTK推送来的原生Camera2应用拍照之后生成的预览图（Thumbnail）居然是马赛克！！

但如果点击预览图之后再退出，就又是正常的。

Camera2对于更新预览图的操作位于：

vendor/mediatek/proprietary/packages/apps/Camera2/host/src/com/mediatek/camera/ui/ThumbnailViewManager.java

这个函数对于传入的位图数据进行最后的处理并显示。

    public void updateThumbnail(Bitmap bitmap) {
        updateThumbnailView(bitmap);
        if (bitmap != null) {
            doAnimation(mAnimationView);
        } else {
            // for security camera not query db.
            mThumbnailView.setImageDrawable(mRoundDrawable);
            mIsNeedQueryDB = false;
        }
    }

vendor/mediatek/proprietary/packages/apps/Camera2/common/src/com/mediatek/camera/common/mode/photo/PhotoMode.java

bitmap就是在这里传进去的。

    public void onPostViewCallback(byte[] data) {
            ... //createBitmapFromYuv
            mIApp.getAppUi().updateThumbnail(bitmap);
        }
        CameraSysTrace.onEventSystrace(POST_VIEW_CALLBACK, false, true);
    }

一步一步追查数据的来源会发现原来位图是通过Camera的YUV数据转换而来。

createBitmapFromYuv -> covertYuvDataToJpeg

可以将covertYuvDataToJpeg前的YUV数据和之后的jpeg数据保存成对应的图片来进行对比会发现，YUV数据是正常的，但是jpeg图片就已经变成了马赛克。问题一定是出在了转换的时候。

vendor/mediatek/proprietary/packages/apps/Camera2/common/src/com/mediatek/camera/common/utils/BitmapCreator.java

    public static byte[] covertYuvDataToJpeg(byte[] data, int imageFormat,
            int yuvWidth, int yuvHeight) {
        byte[] jpeg;
        Rect rect = new Rect(0, 0, yuvWidth, yuvHeight);
        YuvImage yuvImg = new YuvImage(data, imageFormat, yuvWidth, yuvHeight,
                null);
        ByteArrayOutputStream outputstream = new ByteArrayOutputStream();
   
        int jpegQuality = CameraProfile
                .getJpegEncodingQualityParameter(CameraProfile.QUALITY_HIGH);
        yuvImg.compressToJpeg(rect, jpegQuality, outputstream);
        jpeg = outputstream.toByteArray();
        return jpeg;
    }

在这个函数中很明显看到一个控制图片质量的参数jpegQuality，打印这个值发现居然是0。去检查jpegQuality的范围是0-100，很显然只要将参数改成100，问题就解决了。

diff --git a/common/src/com/mediatek/camera/common/utils/BitmapCreator.java b/common/src/com/mediatek/camera/common/utils/BitmapCreator.java
index ac4dcd0..2294301 100755
--- a/common/src/com/mediatek/camera/common/utils/BitmapCreator.java
+++ b/common/src/com/mediatek/camera/common/utils/BitmapCreator.java
@@ -415,9 +415,11 @@ public class BitmapCreator {
         YuvImage yuvImg = new YuvImage(data, imageFormat, yuvWidth, yuvHeight,
                 null);
         ByteArrayOutputStream outputstream = new ByteArrayOutputStream();
+        /*
         int jpegQuality = CameraProfile
                 .getJpegEncodingQualityParameter(CameraProfile.QUALITY_HIGH);
-        yuvImg.compressToJpeg(rect, jpegQuality, outputstream);
+        */
+        yuvImg.compressToJpeg(rect, 100, outputstream);
         jpeg = outputstream.toByteArray();
         return jpeg;
     }

这种方法同样可以控制预览图的质量。