Re: How to convert ZPixMap to BGRA reliably?
On Fri, Aug 25, 2017 at 06:25:41PM +0530, Sai Prasanna wrote:
>I want to get the same values as got by using XGetImage for red_mask,
>blue_mask and green_mask in xcb.
>Here is m C-go lang code.
>I am iterating on the screen got from xcb_setup_roots_iterator .
>for depthIter := C.xcb_screen_allowed_depths_iterator(cx.screen);
>depthIter.rem != 0; C.xcb_depth_next() {
>d := depthIter.data
>for visual_iter := C.xcb_depth_visuals_iterator(d);
>visual_iter.rem != 0; C.xcb_visualtype_next(_iter) {
>v := visual_iter.data
>fmt.Printf("MASKS %x, %x, %x", v.red_mask, v.green_mask,
>v.blue_mask)
>}
>}
>
>Which Depth and Visual Id should I select for getting correct masks ?
Generally, VisualID is inherited from a window you taking con-
tents of.
I mean, if you are casting get_image on a window -- than it is
VisualID of that window, and if you do get_image on a pixmap --
than that pixmap is somehow filled with some data, probably via
XCopyArea, and you should use VisualID of the window you used to
fill that pixmap.
Also, you can fill the pixmap with drawing functions like im-
age_text or poly_line or put_image requests -- than contents of
it's available planes is determined by your colors in GC and/or
your image data.
The Depth should be the same that you used in XCreateWindow or
XCreatePixmap.
>On Wed, Aug 23, 2017 at 6:47 PM, Ilya Anfimov <[1]i...@tzirechnoy.com>
>wrote:
>
> On Tue, Aug 22, 2017 at 11:39:26AM +0530, Sai Prasanna wrote:
> >I thought Zpixmap mapped directly to BGRA. But my assumption didn't
> turn
> >out to be correct in some older X versions.
> >
> >I am using xcb_get_image and xcb_shm_get_image to grab screen
> pixels. I
> >used Zpixmap option for image format. In new-ish Xorg versions it
> works
> >perfectly.
> >
> >But in some machines with older Xorg (1.15 and below) , I get
> discolored,
> >overlapped data, and it is less than 4 * width * height bytes. If I
> try to
> >read with bytes per pixel as 4 , overflow occurs.
> >
> >Could this be some environment issue , or is there any other
> "proper" way
> >to convert Zpixmap to bgra/rgb formats?
>
> 1) The best source of knowledge about core X11 functionality
> is the "X Window System Protocol" book, available e.g. here:
>
>[2]https://www.x.org/docs/XProtocol/proto.pdf
>
> 2) The general pixel storage of the Z pixmap format is described
> there in section 8 (Connection Setup), "Server information" and
> pixel contents -- in "Visual information".
>
> It does not need to be 4 bytes per pixel, or even integer bytes
> per pixel. Number of bits per pixel is specified in FORMAT: field
> of server connection setup response (and may be taken via
> xcb_get_setup in xcb library).
> Many X servers round pixel size up to integer number of bytes,
> as it allows some shortcuts and speedups in server implementa-
> tion, but not all do that.
>
> Pixels does not need to be in {pad,r,g,b} format. The masks for
> red, green and blue are specified in VISUALTYPE: field of server
> connection setup response. Fortunately, that masks are contigu-
> ous, but they don't need to lay on a byte boundary. However,
> modern processors don't care much about bit shift size, and it
> does not matter -- shift by 8 bits or 11.
>
> Also, pixels will be in different byte orders as specified by
> image-byte-order: field in server response. You should prepare to
> access individual bytes, not integers (or find some other solu-
> tion).
>
> It would be good to build you program for something like Debian
> mips architecture (not mips-el!) and check all combinations of
> your program and X server in something like qemu-system-mips.
>
> PS And yes, probably the most recommended ways to read image
> from X11 is to use some image manipulation library, like libgdk
> or imagemagick.
> The required transformations are fairly simple, though, and if
> you are messing with xcb, that it should be really simple to
> write a conversion code in like 30-50 lines.
>
> ___
> [3]xorg@lists.x.org: X.Org support
> Archives: [4]http://lists.freedesktop.org/archives/xorg
> Info: [5]https://lists.x.org/mailman/listinfo/xorg
> Your subscription address: %(user_address)s
>
> References
>
>Visible links
>1. mailto:i...@tzirechnoy.com
>2. https://www.x.org/docs/XProtocol/proto.pdf
>3. mailto:xorg@lists.x.org
>4. http://lists.freedesktop.org/archives/xorg
>5. https://lists.x.org/mailman/listinfo/xorg
>
Re: How to convert ZPixMap to BGRA reliably?
I want to get the same values as got by using XGetImage for red_mask,
blue_mask and green_mask in xcb.
Here is m C-go lang code.
I am iterating on the screen got from xcb_setup_roots_iterator .
for depthIter := C.xcb_screen_allowed_depths_iterator(cx.screen);
depthIter.rem != 0; C.xcb_depth_next() {
d := depthIter.data
for visual_iter := C.xcb_depth_visuals_iterator(d); visual_iter.rem
!= 0; C.xcb_visualtype_next(_iter) {
v := visual_iter.data
fmt.Printf("MASKS %x, %x, %x", v.red_mask, v.green_mask,
v.blue_mask)
}
}
Which Depth and Visual Id should I select for getting correct masks ?
On Wed, Aug 23, 2017 at 6:47 PM, Ilya Anfimov wrote:
> On Tue, Aug 22, 2017 at 11:39:26AM +0530, Sai Prasanna wrote:
> >I thought Zpixmap mapped directly to BGRA. But my assumption didn't
> turn
> >out to be correct in some older X versions.
> >
> >I am using xcb_get_image and xcb_shm_get_image to grab screen pixels.
> I
> >used Zpixmap option for image format. In new-ish Xorg versions it
> works
> >perfectly.
> >
> >But in some machines with older Xorg (1.15 and below) , I get
> discolored,
> >overlapped data, and it is less than 4 * width * height bytes. If I
> try to
> >read with bytes per pixel as 4 , overflow occurs.
> >
> >Could this be some environment issue , or is there any other
> "proper" way
> >to convert Zpixmap to bgra/rgb formats?
>
> 1) The best source of knowledge about core X11 functionality
> is the "X Window System Protocol" book, available e.g. here:
>
> https://www.x.org/docs/XProtocol/proto.pdf
>
> 2) The general pixel storage of the Z pixmap format is described
> there in section 8 (Connection Setup), "Server information" and
> pixel contents -- in "Visual information".
>
> It does not need to be 4 bytes per pixel, or even integer bytes
> per pixel. Number of bits per pixel is specified in FORMAT: field
> of server connection setup response (and may be taken via
> xcb_get_setup in xcb library).
> Many X servers round pixel size up to integer number of bytes,
> as it allows some shortcuts and speedups in server implementa-
> tion, but not all do that.
>
> Pixels does not need to be in {pad,r,g,b} format. The masks for
> red, green and blue are specified in VISUALTYPE: field of server
> connection setup response. Fortunately, that masks are contigu-
> ous, but they don't need to lay on a byte boundary. However,
> modern processors don't care much about bit shift size, and it
> does not matter -- shift by 8 bits or 11.
>
>
> Also, pixels will be in different byte orders as specified by
> image-byte-order: field in server response. You should prepare to
> access individual bytes, not integers (or find some other solu-
> tion).
>
> It would be good to build you program for something like Debian
> mips architecture (not mips-el!) and check all combinations of
> your program and X server in something like qemu-system-mips.
>
>
> PS And yes, probably the most recommended ways to read image
> from X11 is to use some image manipulation library, like libgdk
> or imagemagick.
> The required transformations are fairly simple, though, and if
> you are messing with xcb, that it should be really simple to
> write a conversion code in like 30-50 lines.
>
>
>
>
> ___
> xorg@lists.x.org: X.Org support
> Archives: http://lists.freedesktop.org/archives/xorg
> Info: https://lists.x.org/mailman/listinfo/xorg
> Your subscription address: %(user_address)s
___
xorg@lists.x.org: X.Org support
Archives: http://lists.freedesktop.org/archives/xorg
Info: https://lists.x.org/mailman/listinfo/xorg
Your subscription address: %(user_address)s
Re: How to convert ZPixMap to BGRA reliably?
On Tue, 2017-08-22 at 11:39 +0530, Sai Prasanna wrote: > I thought Zpixmap mapped directly to BGRA. But my assumption didn't > turn out to be correct in some older X versions. > > I am using xcb_get_image and xcb_shm_get_image to grab screen pixels. > I used Zpixmap option for image format. In new-ish Xorg versions it > works perfectly. > > But in some machines with older Xorg (1.15 and below) , I get > discolored, overlapped data, and it is less than 4 * width * height > bytes. If I try to read with bytes per pixel as 4 , overflow occurs. Which machines are these, specifically? In particular, when you run xdpyinfo, you should see a line for the depth-24 pixmap format, like this: depth 24, bits_per_pixel 32, scanline_pad 32 Some older servers may instead have bits_per_pixel == 24, in which case the data is missing the "A" channel, which would explain the buffer overrun you're seeing (which I bet happens at 3 * width * height). Newer servers and drivers attempt to hide 24bpp formats from clients for exactly this reason. - ajax ___ xorg@lists.x.org: X.Org support Archives: http://lists.freedesktop.org/archives/xorg Info: https://lists.x.org/mailman/listinfo/xorg Your subscription address: %(user_address)s
How to convert ZPixMap to BGRA reliably?
I thought Zpixmap mapped directly to BGRA. But my assumption didn't turn out to be correct in some older X versions. I am using xcb_get_image and xcb_shm_get_image to grab screen pixels. I used Zpixmap option for image format. In new-ish Xorg versions it works perfectly. But in some machines with older Xorg (1.15 and below) , I get discolored, overlapped data, and it is less than 4 * width * height bytes. If I try to read with bytes per pixel as 4 , overflow occurs. Could this be some environment issue , or is there any other "proper" way to convert Zpixmap to bgra/rgb formats? ___ xorg@lists.x.org: X.Org support Archives: http://lists.freedesktop.org/archives/xorg Info: https://lists.x.org/mailman/listinfo/xorg Your subscription address: %(user_address)s
