bitmap scanline property (and related question)

[BlakeBlake]

I tried to use the scanline property to get a Pbytearray but the index is out of bounds. I have tried many things but still cant get it to work.
Can somebody give me a demo that shows how to read a bitmap from top to bottom or from left to right? and draw directly onto a form?
Also how would I manipulate the pixels within the quickly?
What is the best way to do this, with a loop? that seems slow to me, what is the best way to manipulate the data in one go with the same manipulation routine?

--thanks

[sun]

if you load pixels of a line with tbitmap.scanline in an array, you have direct access the color to each pixel of line by index.

this works only for 256 color bitmaps, 'cause more colors more informations per pixel.
save your bmp in 256 color mode or convert it programatically. else you must use very hard to understand graphic routines.
i have learned much about these things at torry's delphi pages.

[MrBaseball34]

What exactly are you trying to do? Earl F. Glynn's lab site
is the premier resource for Delphi graphic programming.
www.efg2.com/lab.

Check out the articles on ScanLine there...

[BlakeBlake]

I am experimenting
I am trying to make a screensaver that simulates a lens moving over it.
with a difference
The difference being the lens is a file (grayscale bitmap) and I have a screenshot of the desktop and I want to blend the shaded areas of the alpha channel into the desktop so that I get a nice faded lens. White being total transparency and black having no transparency.
maybe the explanation may help anybody to help me.

I need to know how to blend 2 pictures together using an alpha channel to vary the blending.

Ive even confused myself with this one