The BBitmap class insists that a
BApplication
object be present (but not necessarily running).
| Class Overview |
BBitmap(BRect bounds,
color_space space,
bool acceptsViews = false,
bool needsContiguousMemory = false);
BBitmap(BMessage* archive);
Creates a new BBitmap object that can hold a bitmap whose size and depth
are described by bounds and space.
The bitmap data is uninitialized; you set the data through
Bits() /
SetBits(),
or by drawing into an attached
BView
(see "Using a View to Draw into a Bitmap").
The BBitmap class insists that a
BApplication
object be present (but not necessarily running).
If BViews are to be used,
the acceptsViews argument must be set to true.
Furthermore (in this case), the origin of the bounds rectangle must be
0.0
If the needsContiguousMemory flag is
true, the BBitmap will make sure
that the (physical) memory it allocates is one contiguous physical chunk.
This should matter only to drivers doing direct DMA into physical memory.
The possible color spaces are enumerated in the section "Color Spaces".
virtual ~BBitmap();
Frees all memory allocated to hold image data, deletes any
BViews used to
create the image, gets rid of the off-screen window that held the views,
and severs the BBitmap's connection to the
Application Server.
virtual void AddChild(BView* aView);
Adds aView (and all its children) to this
BBitmap's view hierarchy, and
causes AttachedToWindow()
to be sent to the newly add children.
If aView already has a parent, the application may crash. Be sure to
remove the view from a previous parent before trying to add it to a
bitmap.
AddChild() fails if the BBitmap
was not constructed to accept views.
See also:
BWindow::AddChild(),
BView::AttachedToWindow(),
RemoveChild(),
the BBitmap constructor
virtual status_t Archive(BMessage* archive,
bool deep = true) const;
Calls the inherited version of
Archive() and stores the
BBitmap in the
BMessage archive.
See also:
BArchivable::Archive(),
Instantiate() static function
void* Bits() const;
Returns a pointer to the bitmap data. The length of the data can be
obtained by calling BitsLength()—or it can be calculated from the
height of the bitmap (the number of rows) and
BytesPerRow().
The data is in the format specified by
ColorSpace().
This pointer is valid throughout the entire lifespan of the object.
See also:
Bounds(),
BytesPerRow(),
BitsLength()
int32 BitsLength() const;Returns the number of bytes that were allocated to store the bitmap data.
See also:
Bits(),
BytesPerRow()
BRect Bounds() const;Returns the bounds rectangle that defines the size and coordinate system of the bitmap. This should be identical to the rectangle used in constructing the object.
int32 BytesPerRow() const;Returns how many bytes of data are required to specify a row of pixels. This may include slop space required by the graphics hardware; you should always use this call to determine the width of a row of pixels in bytes instead of assuming that it will be the number of pixels multiplied by the size of a pixel in bytes.
BView* ChildAt(int32 index) const;int32 CountChildren() const;
ChildAt() returns the child
BView at index,
or NULL if there's no child
at index. Indices begin at 0 and count only
BViews that were added to the
BBitmap (added as children of the top view of the BBitmap's off-screen
window) and not subsequently removed.
CountChildren() returns the number of
BViews
the BBitmap currently has.
(It counts only BViews that were added directly to the BBitmap, not
BViews farther down the view hierarchy.)
These functions fail if the BBitmap wasn't constructed to accept views.
color_space ColorSpace() const;
Returns the color space of the data being stored (not necessarily the
color space of the data passed to the
SetBits() function). Once set by
the BBitmap constructor, the color space doesn't change.
Returns the BView
at point within the bitmap or the BView tagged
with name. The point must be somewhere within the
BBitmap's bounds
rectangle, which must have the coordinate origin, (0.0, 0.0), at its left
top corner.
If the BBitmap doesn't accept views, this function fails. If no view
draws at the point given, or no view associated with the BBitmap has the
name given, it returns NULL.
bool IsValid() const;
Returns true if there's memory for the bitmap (if the address returned by
Bits() is valid), and false if not.
bool Lock();void Unlock();bool IsLocked() const;
These functions lock and unlock the off-screen window where
BViews
associated with the BBitmap draw. Locking works for this window and its
views just as it does for ordinary on-screen windows.
Lock() returns false if the BBitmap doesn't accept views or if its
off-screen window is unlockable (and therefore unusable) for some reason.
Otherwise, it doesn't return until it has the window locked and can
return true.
IsLocked() returns false if the BBitmap doesn't accept views. Otherwise,
it returns the lock status of its off-screen window.
virtual bool RemoveChild(BView* aView);
Removes aView from the hierarchy of views associated with the BBitmap,
but only if aView was added to the hierarchy by calling BBitmap's version
of the AddChild() function.
If aView is successfully removed, RemoveChild() returns true. If not, it
returns false.
void SetBits(const void* data,
int32 length,
int32 offset,
color_space mode);
Assigns length bytes of data to the BBitmap object. The new data is
copied into the bitmap beginning offset bytes (not pixels) from the start
of allocated memory. To set data beginning with the first (left top)
pixel in the image, the offset should be 0; to set data beginning with,
for example, the sixth pixel in the first row of a B_RGB32 image, the
offset should be 20. The offset counts any padding required to align rows
of data.
This function is intended to be used for importing existing data from a
different format rather than for setting individual pixels in the bitmap.
If you're interested in coloring individual pixels, use
Bits() to obtain
direct access to the bitmap data.
The source data is specified in the mode color space, which may or may
not be the same as the color space that the BBitmap uses to store the
data. If not, the following conversions are automatically made:
B_GRAY1 and B_RGB32 to B_CMAP8.
B_CMAP8 and B_GRAY1 to B_RGB32.
These are the only color conversions SetBits() understands; all other
conversions must be performed manually.
Colors may be dithered in a conversion to B_CMAP8 so that the resulting
image will match the original as closely as possible, despite the lost
information.
If the color space mode is B_RGB32, the data should be triplets of three
8-bit components—red, green, and blue, in that order—without
an alpha component. Although stored as 32-bit quantities with the
components in BGRA order, the input data is only 24 bits in RGB order.
Rows of source data do not need to be aligned.
However, if the source data is in any mode other than B_RGB32, padding
must be added so that each row is aligned on a int32 word boundary.
SetBits() works only on
BBitmaps in B_GRAY1,
B_CMAP8, and B_RGB32 color
spaces; all other conversions must be carried out manually.
This function works for all BBitmaps, whether or not BViews are also
enlisted to produce the image.
static BArchivable* Instantiate(BMessage* archive);
Returns a new BBitmap object—or NULL, if the archive message
doesn't contain data for a BBitmap object. The new object is allocated by
new and created with the version of the constructor that takes a BMessage
archive.
See also:
BArchivable::Instantiate(),
instantiate_object(),
Archive()
The Archive()
function adds the following fields to its BMessage argument:
| Field | Type code | Description |
|---|---|---|
_frame | B_RECT_TYPE | The BBitmap's bounds rectangle. |
_cspace | B_INT32_TYPE | The color_space of the data. |
_view_ok | B_BOOL_TYPE | Always true, indicating the BBitmap accepts views
(only present in deep copy archives of BBitmaps accepting views). |
_data | B_RAW_TYPE | The bitmap data (present only if _view_ok not present). |
_continguous | B_BOOL_TYPE | Whether the BBitmap requires memory in one
contiguous chunk. |
If the _view_ok field is present, the child views of the BBitmap are
additionally archived in the _views array of
BMessages. See the
description of the BView
Archived Fields for more information on those
fields.