System error capturing the output of a MediaProjection virtual display to an ImageReader

Question

I am working on an application that needs to capture the screen to a bitmap to transmit. I am attempting to use the new Android 5.0 android.media.projection APIs to do the s

Answer 1

A better way to get the Image from ImageReader is just to create right sized bitmap and use the method copyPixelsFromBuffer(). Create ImageReader as follows:

mImageReader = ImageReader.newInstance(mWidth, mHeight, ImageFormat.RGB_565, 2);

Then you can get the image from mImageReader using the code below.

final Image.Plane[] planes = image.getPlanes();
final ByteBuffer buffer = planes[0].getBuffer();
int offset = 0;
int pixelStride = planes[0].getPixelStride();
int rowStride = planes[0].getRowStride();
int rowPadding = rowStride - pixelStride * mWidth;
// create bitmap
bitmap = Bitmap.createBitmap(mWidth+rowPadding/pixelStride, mHeight, Bitmap.Config.RGB_565);
bitmap.copyPixelsFromBuffer(buffer);
image.close();

I have described the process of capturing screen using MediaProjection API along with the mistakes most people made when getting image from ImageReader in a blog post which you can read if interested.

Answer 2

I think I can answer this question now, I met the same problem and after I change ImageFormat.JPEG to PixelFormat.RGBA_8888 everything goes well. It seems ImageFormat.JPEG is not supported.

You need to use the following code to get the correct bitmap:

                    int width = img.getWidth();
                    int height = img.getHeight();
                    int pixelStride = planes[0].getPixelStride();
                    int rowStride = planes[0].getRowStride();
                    int rowPadding = rowStride - pixelStride * width;
                    byte[] newData = new byte[width * height * 4];

                    int offset = 0;
                    bitmap = Bitmap.createBitmap(metrics,width, height, Bitmap.Config.ARGB_8888);
                    ByteBuffer buffer = planes[0].getBuffer();
                    for (int i = 0; i < height; ++i) {
                        for (int j = 0; j < width; ++j) {
                            int pixel = 0;
                            pixel |= (buffer.get(offset) & 0xff) << 16;     // R
                            pixel |= (buffer.get(offset + 1) & 0xff) << 8;  // G
                            pixel |= (buffer.get(offset + 2) & 0xff);       // B
                            pixel |= (buffer.get(offset + 3) & 0xff) << 24; // A
                            bitmap.setPixel(j, i, pixel);
                            offset += pixelStride;
                        }
                        offset += rowPadding;
                    }

From this way, the content of bitmap is what you want.

PS: I really want to say, the doc of android is pretty bad. we need to investigate too much detail to use sdk api correctly.