C I Knowles (msczcik@scs.leeds.ac.uk)
Thu, 22 Jul 1999 10:38:45 +0100
Following on from below and assuming I've installed the patch to make
dataScaleRange work correctly is there any difference, in terms of
performance etc in the order that ...
voAppearanceActions::dataScaleRange(brick, loValue, hiValue);
and
voAppearanceActions::dataConvert(brick, vdata,diskDataFormat);
are called?
Thanks
Chris
On Wed, 21 Jul 1999, C I Knowles wrote:
> I wondered if anyone could explain the following:
>
> I might be being stupid and its only a small mistake but....
>
> I've been experimenting with using a look up table with datasets of
> different types and have some strange results (voRenderingMode is
> MONOCHROME). When using voDataType of BYTE there are no problems - the
> CT.Head.Small.char.tif dataset is displayed correctly with the look up
> table disabled and enabled.
>
> However, to extend my code I want it to be able to cope with data of
> different types. Hence I used the same dataset (CT.Head.Small.char.tif)
> and changed it to float, before copying into the bricks. My code
> actually receives a pointer to the data which is in memory already -
> I've written a routine to copy it into the bricks.
>
> So the data which I'm sticking in the bricks is of type FLOAT and is
> between 256 and 0 as all I've done is cast it. The following occurs...
>
> With the lookuptable disabled I get a mess.... the head is just about
> there but there are obvious problems with grey level values. What seems
> to be happening is grey levels are assigned for 0 to 1 properly but not
> for values greater than 1. This should be expected I believe. To check
> this I cast the data to type float as before and also scaled it to
> between 0 and 1 manually before reading into the bricks, the head is
> then displayed correctly. Hence when using voDataType float it works if
> values are between 0 and 1.
>
> So I thought I should now be able to load the float data into the bricks
> with values between 0 and 256, scale it to between 0 and 1 using the
> 'voAppearanceActions::dataScaleRange' method and get the same results.
> But I don't......(see attached pic1.gif). It looks as though the grey
> levels are assigned before the data is scaled to between 0 and 1, like
> before. If this is the case what is the use of the
> 'voAppearanceActions::dataScaleRange' method? Or am I making a mistake?
>
>
> Thanks,
>
> Chris
>
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