Good day!
I am working on pixel based drawing tool, and could use some hint on
how to handle selection areas.
In the program, each document has a couple different Bitmap context
(24 bit RGP space CGBitmapContext ) at the same time. I draw into a
scroll view using a Layer (CGLayer). Whenever one of the bitmap
context changes, I copy the changes into the layer, but scrolling
within the view is done only with the layer except for drawing the
selection area.
As always, I want to make sure there isn't a better way of doing what
I am doing now.
To handle the selection, I have been using a CGBitmapContext (created
with method CGBitmapContextCreate with a bitsPerComponent of 8, a
color space of GreySpace, and CGBitmap info of kCGImageAlphaNone).
This gives me an editable context, so that I can create the selection
graphic using Quartz draw rectangles and ovals. When I need to draw
using the selection, I convert the selection into an image
(CGBitmapContextCreateImage), clip the context to that image
(CGContextClipToMask) and then do whatever drawing I want to do (ex.
invert, special fill, you name it).
First of all, it is possible to create a single bit bitmap context
(only black and white)? I could only get 8 bit greyscale working
correctly.
Should I be using ImageMask for these operations? I did not create a
bitmap mask (using CGImageMaskCreate) because I needed to be able to
constantly modify the mask using rectangle and oval commands (and I
could not get that call to work).
Lastly, when when drawing between bitmap context (basically copying
one section to another), is the best way to create an Image from the
bitmap info (CGBitmapContextCreateImage) and then draw using the
image. Apple documentation suggest that this is quick enough. If I
create an image, and then modify the context, the image I created
would have a copy of the data, not any changes.
Thanks for any comments!
Steve Sheets
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