On Sun, 19 Nov 2006, Steffen wrote:
> Hi,
>
> I am looking for comments on the following code fragments that I am
> using for the drawing of datatype image objects. It's not 100% MUI
> related since it is independent of MUI but since there are some good
> experts present on this list I thought I ask here. I would like the
> code to work with current and previous versions of datatypes.library
> and also supporting transparent colors where possible.
>
> I devided the code into 4 sections: loading of an image, performing
> display related stuff, drawing, and freeing of the object.
>
> 1. Loading a datatypes object is done prior to having any information
> about the display environment. I am using the following:
>
> Object *dto = (Object *)NewDTObject((char *)filename,
> DTA_GroupID, GID_PICTURE,
> PDTA_DestMode, PMODE_V43,
> OBP_Precision, PRECISION_EXACT,
> PDTA_Remap, FALSE,
> TAG_DONE);
>
> I am unsure here about OBP_Precision and PDTA_Remap. From the NDK3.9
> autodocs I find that their applicability are both [I..] so I can only
> place them here but I don't know what these tags really do. The
> meaning of OBP_Precision seems relatively clear but the docs for
> PDTA_Remap are somewhat unclear to me. Anybody knows more?
IIRC PDTA_Remap defaults to TRUE. When enabled images are remapped to
target screen.
> 2. Once we know the display environment (e.g. in MUIM_Setup) I am
> continuing like this (obj is my custom-class MUI object):
>
> SetAttrs(dto,
> PDTA_Screen, _screen(obj),
> PDTA_UseFriendBitMap , TRUE,
> TAG_DONE);
>
> I am wondering if SetAttrs is the correct way to do this since there
> is also SetDTAttrs but the latter also requires a window and a
> requester parameter. Any idea?
I have no idea. I recall you can pass NULL window/requester but using
SetAttrs() should be ok.
(You could add PDTA_FreeSourceBitMap, TRUE but then you lose original
bitmap.)
> The next steps from here are copied from some source that was posted
> on this list a long time ago by Stefan (if I remember correctly, they
> seem not to be in the mailing list archive):
>
> struct FrameInfo fri = { 0 };
> struct BitMapHeader *bmh = NULL;
> struct BitMap *bm = NULL;
>
> DoMethod(dto, DTM_FRAMEBOX, NULL,
> &fri, &fri, sizeof(struct FrameInfo), 0);
Not needed.
> if (fri.fri_Dimensions.Depth > 0) {
> if (DoMethod(data->d_Object, DTM_PROCLAYOUT, NULL, 1)) {
> bmh = pget(data->d_Object, PDTA_BitMapHeader);
> if (bmh) {
> GetDTAttrs(dto, PDTA_DestBitMap, &bm, TAG_DONE);
> if (!bm) {
> GetDTAttrs(dto, PDTA_BitMap, &bm, TAG_DONE);
Getting PDTA_BitMap not needed, getting PDTA_DestBitMap cant fail here.
> }
> }
> }
> }
>
> I am not sure what all these functions do as the autodocs on them are
> quite too short. E.g. for DTM_PROCLAYOUT you only find: "Layout
> (remap) the picture on the application's process." I also don't know
DTM_PROCLAYOUT in practise produces PDTA_DestBitMap.
> what is the difference between GetAttrs (from intuition.library and
> used in the pget call above) and GetDTAttrs?
I'd like to know too :P
> 3. Now we can draw the object. Starting with V44 there is a method
> that we can use directly. So I continue in the following way:
>
> BOOL success = FALSE;
>
> if (DataTypesBase->lib_Version >= 44) {
> APTR handle = ObtainDTDrawInfoA(dto, TAG_DONE);
> if (handle) {
> success = DrawDTObjectA(_rp(obj), dto,
> x, y, w, h, 0, 0, TAG_DONE);
> ReleaseDTDrawInfo(dto, handle);
> }
> }
>
> if (!success) { /* draw with pre V44 functions */
> APTR mask = NULL;
> GetDTAttrs(dto, PDTA_MaskPlane, &mask, TAG_DONE);
> if (mask) {
> BltMaskBitMapRastPort(bm, 0, 0, _rp(obj),
> x, y, w, h, 0xc0, mask);
> } else {
> BltBitMapRastPort(bm, 0, 0, _rp(obj), x, y, w, h, 0xc0);
> }
> }
>
> I am wondering if there is any difference in using the new V44 method
> and the one I am using for pre V44. It might be that V44 has some
> capabilities for alpha blending. Is it worth checking for V44 or
> would the fallback code work equally well?
I doubt alpha blending is supported.
> Last but not least I would like to know from which version of
> datatypes.library on transparent colors (the mask plane) are
> supported. V40 seems to always give me a NULL mask, so I guess one
> needs V43 or better?
>
> 4. The last step is too free the datatypes object once we don't need
> it anymore. I simply call DisposeDTObject(dto) and assume that all
> pointer I got the the object (BitMapHeader, BitMap, Mask) are freed by
> the datatypes object itself.
That is correct.
Btw since you are using MUI and datatypes to view images why not just use
DtpicObject? :)
image = DtpicObject("image.png", TAG_DONE);
Greets, Ilkka
Visit http://www.amiga.dk/tumult for MUI-related
information, especially about MUI custom classes.
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