On Sunday October 12 2003 17:41, Russell Valentine wrote:
> I'm having trouble sometimes figuring out what Python datatype
> goes with the C++ datatype.
>
> An example a 2x2 grayscale QImage:
>
> **C++ Define
>
> QImage ( uchar * yourdata, int w, int h, int depth, QRgb *
> colortable, int numColors, Endian bitOrder )
>
>
> How do you know what type to use for uchar *yourdata?
>
> **Python?
>
> grayColorMap = []
> for i in range(256):
> grayColorMap.append(QColor(i, i, i).rgb())
>
> buffer = []
> buffer.append(255) #white
> buffer.append(0) #black
> buffer.append(255) #white
> buffer.append(0) #black
>
> image = QImage(buffer, 2, 2, 8, grayColorMap, 256,
> QImage.IgnoreEndian)
>
>
> But I get:
>
> Traceback (most recent call last):
> File "./testQColor.py", line 22, in ?
> image = QImage(buffer, 2, 2, 8, grayColorMap, 256,
> QImage.IgnoreEndian) File
> "/usr/lib/python2.2/site-packages/qt.py", line 439, in
> __init__ libqtc.sipCallCtor(123,self,args)
> TypeError: Too many arguments to QImage(), 1 at most expected
>
>
> I am confused. Thanks for any help!
Here is the method referenced from the PyQt docs:
"""
QImage(uchar *data, int w, int h, int depth, QRgb *colorTable,
int numColors, Endian bitOrder);
The colorTable parameter is a list of QRgb instances or None. (Qt
v2.1+)
"""
This probably won't clarify the uchar* parameter for you, but it
does indicate that the QRgb* parameter is a Python list of
QRgb instances or None.
>From the C++ code in sipqtQImage.cpp, here's some of the actual
code your Python constructor call will execute:
uchar *a0;
int a1;
int a2;
int a3;
PyObject *a4;
int a5;
int a6;
if (sipParseArgs (&sipArgsParsed, sipArgs, "siiiNie",
&a0,&a1,&a2,&a3,&PyList_Type,&a4,&a5,&a6))
>From the type for a0 (and the "s" in the format string -
the complete format string is "siiiNie"), "yourdata" is simply a
Python string. a4 is the Python list of QRgb instances.
The reason you're getting the error message about "too many
arguments" is that there is a constructor that takes a list
of strings as its only argument, and the code thinks you're
calling that constructor..
You want 'buffer' to be a Python string, not a list to call the
constructor you're calling. I haven't needed to figure out how
to put 8 bit chars into a string efficiently, but you can do
things like:
buffer = "a" + chr (255)
or
buffer = "a\xff"
I think Detlev draws some icons in some of the eric Python code -
I'm not sure if they're QImages, but the method should be
similar. If you have eric, you can take a look at that.
Jim
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