Mattias Gaertner wrote:
On Tue, 17 Apr 2007 11:07:59 +0200
Marc Weustink <[EMAIL PROTECTED]> wrote:
Mattias Gaertner wrote:
On Tue, 17 Apr 2007 10:24:36 +0200
Marc Weustink <[EMAIL PROTECTED]> wrote:
Mattias Gaertner wrote:
On Mon, 16 Apr 2007 22:46:49 +0200
Marc Weustink <[EMAIL PROTECTED]> wrote:
Mattias Gaertner wrote:
On Mon, 16 Apr 2007 11:20:55 +0200
Marc Weustink <[EMAIL PROTECTED]> wrote:
Continuing my TRawImageQuestion.
While implementing cursors and imagelists, Paul and I start to
get confused. It appears that Mask and Alpha are treated as
equal while in fact they are each others inverse. (An 1 in a
mask means that this part of the image is masked, not drawn,
where for alpha a 1 means opaque, fully drawn)
A RawImageDesription describes the RGB and Alpha parts of an
image. It has also a flag that the Alpha is separate. This got
introduced since traditional windows has only an image and a
(1bpp) mask. When reading such image, the mask gets converted
into a 1bit separate alpha.
With CreateBitmapFromRawImage the fun starts. It creates a
bitmap and mask handle form the rawimage. The maskhandle is
created from the (separate) alpha and is in fact returning an
alpha handle and not a maskhandle. On win32 this is nonsense
since alpha is never separated. So I think a Maskhandle should
return what it means: a handle to a Mask (and only in the case
when the description had the AlphaSeparate flag).
Comments ?
Maybe we need an enum, how to interpret the alpha value?
I was think on that also, but somehow didn't sound right. I don't
know exactly for all widgets, but as far as I can tell the
separate alpha is only used for win32 1bit masks.
If this is the case, then ignore my other mail since
TRawImage.MaskData is indeed MaskData. But then the
AlphaSeparate, AlphaBitsPerPixel, AlphaLineEnd, AlphaBitOrder
and AlphaByteOrder are not really Alpha, but Mask ->
MaskSeparate (or HasMask), MaskBitsPerPixel, MaskLineEnd,
MaskBitOrder and MaskByteOrder
True.
What do we take instead of the enum?
define: if Mask is separate, then it is opacity, otherwise
transparency?
Something like that. But IMO there is no such thing as
MaskIsSeparate since there won't be an included mask. HasMask is a
better name I think.
ok. Will you change it?
Yes.
And if we add MaskPrec and MaskShift: cardinal; then the Alpha
definition is complete independent of a Mask definition
Ehm, but they are not independent, are they? You can not have both!?
It is a bit useless, but technically there is imo no limitation.
And for naming it becomes clear what is meant. Mask for Mask and
Alpha for alpha. Thinking of it, when having a MaskPrec=0 it means
the same as HasMask=False
True.
BTW, why are the xxxPrec and xxxShift defined as Cardinal and not
byte ?
Why should they?
Since I think a 1000000 bit precision and a 123456789 shift won't be
needed.
You will only save the memory by using packed or an array. With packed
we will loose speed and with an array loose readability.
No
if you declare a record like
TMyRecord = record
field1: Cardinal;
field2: Byte;
field3: Byte;
field4: Byte;
field5: Cardinal;
end;
then the record is aligned on a cardinal boundary and field2..4 are
aligned on a byte boundary, without the need for packing.
field5 is aligned to a cardinal boundary again.
The example here only occupies 12 bytes, without speed degradation.
I was even considering in making them an enum, so some
lookups could be made easier and some range checking can be avoided
I don't see, how you can avoid range checking?
If you define a lookup array[0..15] you dont have to check if Prec will
be larger than 15 for instance.
Marc
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