Hi Davide, I have already reply to you on the dedicated ticket. I duplicate here my answer.
I have tried the solution of erasecolor, but it doesn't work.
This is the piece of code that we use for render pdf:
Matrix matrix = new Matrix();
matrix.postScale(width / pageBounds.width(), height / pageBounds.height());
matrix.postTranslate(pageSliceBounds.left * width, pageSliceBounds.top * height);
matrix.postScale(1 / pageSliceBounds.width(), 1 / pageSliceBounds.height());
final float[] matrixSource = new float[9];
matrix.getValues(matrixSource);
DIB dib = new DIB();
dib.CreateOrResize(width, height);
float ty = (float) Math.floor(actualHeight * matrixSource[4] - matrixSource[5]);//+1;
com.radaee.pdf.Matrix mat = new com.radaee.pdf.Matrix(matrixSource[0], -matrixSource[4], -matrixSource[2]-0, ty);
RenderPrePare(dib);
Render(dib, mat);
mat.Destroy();
Bitmap bitmap= Bitmap.createBitmap( width, height, Config.ARGB_8888);
bitmap.eraseColor(0xFF0000FF); // try with any color
BMP bmp = new BMP();
bmp.Create(bitmap);
dib.DrawToBmp(bmp, 0, 0);
bmp.Free(bitmap);
dib.Free();
Many thanks.