I need help doing a diagonal gradient

General
1

I can do a diagonal gradient from left to right but can’t get a right to left. I’m sure its simple but I have struggled for an hour trying to figure it out. Please have a look at the code below. :slight_smile:

[code]Dim startColor As Color = &c33333300
Dim endColor As Color = &c80808000

Dim p as New Picture(5, 5)
Dim samt, eamt As Double

For i As Integer = 0 To p.Height
samt = 1 - (i / p.Height)
eamt = i / p.Height
p.Graphics.ForeColor = RGB((startColor.Red * samt) + (endColor.Red * eamt), _
(startColor.Green *samt) + (endColor.Green * eamt), _
(startColor.Blue * samt) + (endColor.Blue * eamt))

if not doReverse then
  p.Graphics.DrawLine(i, 0, 0, i)//<<<--- this is working the way I expect it to.
else
  p.Graphics.DrawLine(p.Width , i, p.Width-i, p.Height-i)//<<<--- I can't get this to do a reverse version of the diagonal gradient here. 
  
end if

Next[/code]

2

5 x 5? why bother drawing it? why not just make a PNG or JPG and use that?

but here is the code

p.graphics.DrawLine(p.graphics.Width , i, i, p.graphics.Height)

Also… it (true/false both) do not FILL the rectangle… just a 45deg slice… but I assume that is what you want

3

Thank you for the code Dave. Correct. I do not want to fill the rectangle.

I never considered using a png or jpg. I have always drawn my own shadows and such in code.

4

Do a rectangular gradient, then rotate it. MBS and Studio Stable Graphics have fast, high quality, cross platform free rotation functions.

5

On the Mac you can use NSGradient or CGGradient (declares should be done in the MacOSLib). If you’ve never used either CG or NS before, it can be a little daunting, however you can do gradients at any angle and incredibly fast. Even circular gradients.

6

I think this chunk of code will do the trick. It draws the shadow in the upper right-hand corner:

[code] dim g as graphics

g=p.graphics

For i As Integer = 0 To g.Height
samt = 1 - (i / g.Height)
eamt = i / g.Height
g.ForeColor = RGB((startColor.Red * samt) + (endColor.Red * eamt), _
(startColor.Green *samt) + (endColor.Green * eamt), _
(startColor.Blue * samt) + (endColor.Blue * eamt))

if not doReverse then
  g.DrawLine(i, 0, 0, i)//<<<--- this is working the way I expect it to.
else
  g.DrawLine(g.Width-i, 0, g.width, i)//<<<--- I can't get this to do a reverse version of the diagonal gradient here.
end if

Next
[/code]

Note that I declared a Graphics object and assigned p.graphics to it. This makes the code easier to read and more flexible; you can take this code and drop it into any Paint event and have it work. It might also be marginally faster this way (very, very marginally).