YUV420888 to Grayscale Image (cvtColor ENUM) [closed]

asked 2016-11-10 01:02:30 -0500

antdroid gravatar image

updated 2016-11-10 03:08:42 -0500

I looked around for a Conversion of the YUV420 Image to a Grayscale Image and found this Issue in the DevZone

According to this, there is already a YUV to Grayscale Conversion enum for cvtColor(). But, as also mentioned in the issue, the enums are not good documented. My Question now is, which of these Enums do I have to use if I want to convert a packed YUV ByteBuffer into a Grayscale ByteBuffer or Image/cv::Mat?

Thanks for your attentiveness.

So I found the following ENUM CV_YUV2GRAY_420 is that the one I need?

I tried the enum above with this test:

I capture a Frame in Android from my Preview in YUV_420_888Format. I pass that to a function which packs the 3 Plane buffers into one ByteBuffer and put it into a byte[]:

 Image img = params[0];
 ByteBuffer dstBuffer = ByteBuffer.allocateDirect(img.getWidth() * img.getHeight() * ImageFormat.getBitsPerPixel(img.getFormat()) / 8);

  getDataFromImage(img, dstBuffer);

  byte[] data = new byte[dstBuffer.remaining()];

Then I'll pass that byte[] to JNI and use cv::Mat(height + height/2, width, CV_8UC1, imageData) to create a Mat with the data (the byte[]was converted to a unsigned char*) Now I do this:

cv::Mat img(height + height/2, width, CV_8UC1, imageData)
cv::Mat gry;

cv::cvtColor(img, gry, CV_YUV2GRAY_420, 1)

But it seems, that the result is wrong, because I can't extract any Features out of this grayscale Image.

edit retag flag offensive reopen merge delete

Closed for the following reason question is not relevant or outdated by sturkmen
close date 2020-10-18 14:14:32.579516