how can i extract a bitmap from a PICT?

[John Elemans]

Hello,

I need to save single frames from a Quicktime video stream. I can
grab individual frames with GrabPict(..) which works. Under OS 9
I draw the PICT to an offscreen port and then copybits the image
to a buffer. But the offscreen port is locked under Carbon.

Does anyone know how I can get the bits out under Carbon?
TIA.

je

[John Elemans]

I'm trying to go from picture to pixmap. I'm using DrawPict to an
offscreen port, but all I get are black boxes!

Here's what I'm doing;

osErr = SGGrabPict(gSeqGrabber,&ph,&boundsRect,32,grabFlag s);

SetRect(&boundsRect,0,0,640,480);

qdResult = NewGWorld(&osWorld8,0,&boundsRect,NULL,NULL,noNewD evice);
osWorld8PixMapHandle = GetGWorldPixMap(osWorld8);

lockPixResult = LockPixels(osWorld8PixMapHandle);

myGWFlags = UpdateGWorld (&osWorld8, 8, &boundsRect, NULL,
device1Handle, clipPix);

(*osWorld8PixMapHandle)->pixelType = 0;
(*osWorld8PixMapHandle)->pixelSize = 8;
(*osWorld8PixMapHandle)->cmpCount = 1;
(*osWorld8PixMapHandle)->cmpSize = 8;

(*osWorld8PixMapHandle)->rowBytes = ((( 8 * 640 + 15) >> 4) << 1
) | 0x8000;

SetGWorld(osWorld8,NULL);

DrawPicture(ph,&boundsRect);

BlockMove((*osWorld8PixMapHandle)->baseAddr,(Ptr)buffer,640L*480);

This should, I think, get me the pixmap in my buffer. Under OS 9, I do
something very similar with an offscreen port instead of a GWorld and it
works fine.

TIA.

In article <BB66969A.6C83%mike@objc-source.-DELETE-.org>,
Mike Kluev <mike@objc-source.-DELETE-.org> wrote:

> in article [email]jelemans-48A531.15200613082003@shawnews.vc.shawcable.net[/email], John
> Elemans at [email]jelemans@macpacs.com[/email] wrote on 14/08/2003 02:20:
>

> > I need to save single frames from a Quicktime video stream. I can
> > grab individual frames with GrabPict(..) which works. Under OS 9
> > I draw the PICT to an offscreen port and then copybits the image
> > to a buffer. But the offscreen port is locked under Carbon.

>
> What do you mean by this? To go from picture to pixmap use
> DrawPicture. To go from pixmap to picture use OpenPicture/
> CopyBits/ClosePicture.

[Tom Dowdy]

In article <jelemans-999A67.13470418082003@shawnews.vc.shawcable.net>,
John Elemans <jelemans@macpacs.com> wrote:

> qdResult = NewGWorld(&osWorld8,0,&boundsRect,NULL,NULL,noNewD evice);
> osWorld8PixMapHandle = GetGWorldPixMap(osWorld8);
>
> lockPixResult = LockPixels(osWorld8PixMapHandle);
>
> myGWFlags = UpdateGWorld (&osWorld8, 8, &boundsRect, NULL,
> device1Handle, clipPix);

UpdateGWorld can easily change the pixmap being used for the GWorld.
Your osWorld8PixMapHandle is probably no longer legal, and also unlocked
at this point.

Why not simply create the GWorld at the desired depth (8) rather than 0
in the first place?

> (*osWorld8PixMapHandle)->pixelType = 0;
> (*osWorld8PixMapHandle)->pixelSize = 8;
> (*osWorld8PixMapHandle)->cmpCount = 1;
> (*osWorld8PixMapHandle)->cmpSize = 8;
>
> (*osWorld8PixMapHandle)->rowBytes = ((( 8 * 640 + 15) >> 4) << 1
> ) | 0x8000;

Modifying the pixmap handle that belongs to the GWorld isn't a good
idea, and isn't needed UpdateGWorld has in fact change things for you.

> SetGWorld(osWorld8,NULL);
>
> DrawPicture(ph,&boundsRect);
>
> BlockMove((*osWorld8PixMapHandle)->baseAddr,(Ptr)buffer,640L*480);

This blockmove assumes that the rowBytes are == the depth * the width.
This is an invalid assumption.

[Mike Kluev]

In Article [email]jelemans-999A67.13470418082003@shawnews.vc.shawcable.net[/email], John
Elemans wrote:

> I'm trying to go from picture to pixmap. I'm using DrawPict to an
> offscreen port, but all I get are black boxes!
>
> Here's what I'm doing;
>
> osErr = SGGrabPict(gSeqGrabber,&ph,&boundsRect,32,grabFlag s);
>
> SetRect(&boundsRect,0,0,640,480);
>
> qdResult = NewGWorld(&osWorld8,0,&boundsRect,NULL,NULL,noNewD evice);
> osWorld8PixMapHandle = GetGWorldPixMap(osWorld8);
>
> lockPixResult = LockPixels(osWorld8PixMapHandle);
>
> myGWFlags = UpdateGWorld (&osWorld8, 8, &boundsRect, NULL,
> device1Handle, clipPix);
>
> (*osWorld8PixMapHandle)->pixelType = 0;
> (*osWorld8PixMapHandle)->pixelSize = 8;
> (*osWorld8PixMapHandle)->cmpCount = 1;
> (*osWorld8PixMapHandle)->cmpSize = 8;
>
> (*osWorld8PixMapHandle)->rowBytes = ((( 8 * 640 + 15) >> 4) << 1
> ) | 0x8000;
>
> SetGWorld(osWorld8,NULL);
>
> DrawPicture(ph,&boundsRect);
>
> BlockMove((*osWorld8PixMapHandle)->baseAddr,(Ptr)buffer,640L*480);
>
> This should, I think, get me the pixmap in my buffer. Under OS 9, I do
> something very similar with an offscreen port instead of a GWorld and it
> works fine.

I guess the end result you want to achieve is buffer of pixel values,
not offscreen itself. Instead of the above (which is wrong in many
different ways) try the following:

//allocate buffer to hold 640*480 bytes

SetRect(&r, 0, 0, 640, 480);
err = NewGWorldFromPtr(&offscreen, 8, &r, NULL, NULL, 0, buffer, 640);
// check for error
GetGWorld(&savedPort, &savedDevice);
SetGWorld(offscreen, NULL);
EraseRect(&r);
DrawPicture(pict, &r);
SetGWorld(savedPort, savedDevice);
DisposeGWorld(offscreen);

Also, ensure that grabbed picture is really what you think it is.

--
Mike Kluev

PS. Remove "-DELETE-." part of my e-mail address to reply.