Example image manipulations with little bug
lazarus / 39-Graphics

----------------------------------------------------------------------
xinyiman · 2019-11-06 11:10

Hi guys, for a recent job I had to develop a library to implement the
most common image manipulations. That's why I created a public project
on GitHub at

https://github.com/XinYiMan/simple_image_manipulation

I tested on Mac OS X and apart from a mismatch on the manipulation of
the gamma value seems to work well.
So if someone were to serve, he didn't reinvent the wheel all the
time.

The problem is in the manipulation of the gamma value. If I take an
image and do the gamma encoding it works fine. If I then apply the
decode gamma immediately it seems to not work. But if I result from
the encode gamma save it on a file which I then re-import and apply
the decode range then it works. I don't understand why. Who explains
to me what is wrong?

----------------------------------------------------------------------
xinyiman · 2019-11-06 11:16

My image gamma manipulation test

----------------------------------------------------------------------
circular · 2019-11-06 13:36

Hi,

After writing directly to pixel data, you need to call
InvalidateBitmap. On MacOS, it won't work otherwise because the pixel
data is not linked to the bitmap handle.

Note that using Canvas property is not recommended as it requires
copying from the bitmap handle and vice versa. Also the alpha channel
is not well supported by Canvas.

For example, to copy a part, you can directly use the GetPart
function. Otherwise if you want functions that are Canvas-like, you
can safely use CanvasBGRA property instead.

Regards

----------------------------------------------------------------------
xinyiman · 2019-11-06 13:50

Quote from: circular on November 06, 2019, 02:36:38 pmHi,

After writing directly to pixel data, you need to call
InvalidateBitmap. On MacOS, it won't work otherwise because the pixel
data is not linked to the bitmap handle.

Note that using Canvas property is not recommended as it requires
copying from the bitmap handle and vice versa. Also the alpha channel
is not well supported by Canvas.

For example, to copy a part, you can directly use the GetPart
function. Otherwise if you want functions that are Canvas-like, you
can safely use CanvasBGRA property instead.

Regards
Thank you. With InvalidateBitmap after pixel editing run correctly on
Mac OS X.