Why Does My Java Bitmap Conversion to a Byte Array Result in All 0s?

Byte Array Conversion from Java Bitmap Reevaluated

In an attempt to convert a Java bitmap to a byte array, a developer encounters a peculiar issue where the resultant byte array contains all 0s despite the bitmap being acquired from the camera.

The code snippet employed for this conversion involved extracting the bitmap's row bytes, height, and allocating a ByteBuffer of the calculated size. CopyPixelsToBuffer was then utilized to transfer image data into the buffer, followed by byte extraction into a newly created byte array.

Upon examination, the code seems sound. However, the underlying issue lies in the immutability of the bitmap. Although copyPixelsToBuffer intends to make a copy of the bitmap's data, the underlying image remains unchanged due to its immutability, resulting in a buffer filled with 0s.

An alternative approach offers a definitive solution:

ByteArrayOutputStream

To effectively convert the bitmap into a byte array, consider employing ByteArrayOutputStream along with Bitmap's compress method. This technique compresses the bitmap into a specific format (PNG in this case) and writes the compressed data into a byte array. Subsequently, the bitmap can be recycled to free memory.

By implementing this strategy, you can reliably convert a Java bitmap into a byte array, resolving the issue encountered with copyPixelsToBuffer and producing a valid array of bytes representing the image.

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