|Debian, python 2.5.4, PyQt4 V4.6
In compiled C module trying to copy QImage alpha to 8-bit buffer.
Function called from separate QThread.
Problem in wrong buffer data shifted 29 bytes back.
When doing operation completely in main thread or in calling thread, or doing
image.pixel() >> 24, alpha data is ok.
Alpha extraction function:
///////////////////////////////////////////////////////////////////////////////////////////////////////////
// Get image alpha mask to byte buffer.
// input: QImage image.
// output: str maskBuf.
static PyObject *gray_c32GetAlphaMask(PyObject *self, PyObject *args) {
PyObject *image; // input ARGB32 QImage
// parse function parameters
if (!PyArg_ParseTuple(args, "O", &image)) return NULL;
// get image width and height
U32 w = PyInt_AsLong(PyObject_CallMethod(image, "width", NULL));
U32 h = PyInt_AsLong(PyObject_CallMethod(image, "height", NULL));
if (w*h > 0) {
// pointer to first color pixel
U32 *c32Buf = PyCObject_AsVoidPtr(PyObject_CallMethod(PyObject_CallMethod((PyObject *)image,
"bits", NULL), "ascobject", NULL));
U8 *maskBuf = PyMem_Malloc(w * h); // allocate output buffer
for (U32 yCnt=0; yCnt<h; yCnt++) { // y loop
for (U32 xCnt=0; xCnt<w; xCnt++) { // x loop
*maskBuf = *c32Buf >> 24; // get pixel alpha value
c32Buf++;
maskBuf++;
}
}
return Py_BuildValue("s#", maskBuf, w*h);
}
return Py_BuildValue("O", Py_None);
}
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