HARD!! getting/changing data in bitmap image

Hi experts,
     I have a question that should set you thinking.

     I have a bitmap(a picute I took with a digital camera) that has some writing on it, well its a picture of some writing.  The problem with the photo is that the background is a kind of yucky grey/brown colour, though i wrote it on a clean WHITE peice of paper.

I want to write a program that makes the background colour a colour of the users choice.

I don't even know where to start writeing this, can some one help?

thanx,
     Boyidiot
BoyidiotAsked:
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cool12399Connect With a Mentor Commented:
Also...

Just so you are aware -- the programming task will be a little more challenging than you think,
you will either need a little bit of mathematics background, or someone who does. The image
will not have a 'uniform' yellow color, so you will have to test for tolerance as well if you use
some kind of flood fill routine, which means you'll have to write your own routine to make it
look right. Otherwise -- what you'll see -- is basically an image, still with some yellow, and some
of the yellow pixels whited out. And you can't simply change all 'yellow' pixels, in case the 'image'
has yellow color in it...

So it'll be a little harder than you expect.
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eliaslopezgtzConnect With a Mentor Commented:
try using the win32 api...
setpixel... getpixel...
that would be the fastest way to do ...
but you need to get used to handles.. and things like that...
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BoyidiotAuthor Commented:
yes I could do that I could get the user to select the back colour on the picture then change/blankout all the pixels with that colour, but the background colour isn't the same colour.

hmmm, I could get the user to select the text colour(at its lightest), then only keep the pixels that are darker than it.

Could you help me put it into code, I dont know how to use Setpixel/getpixel.
thanx

 Boyidiot
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eliaslopezgtzCommented:
Public Declare Function ExtFloodFill Lib "gdi32" (ByVal hdc As Long, ByVal x As Long, ByVal y As Long, ByVal crColor As Long, ByVal wFillType As Long) As Long
Public Declare Function GetPixel Lib "gdi32" (ByVal hdc As Long, ByVal x As Long, ByVal y As Long) As Long
Public Type POINTAPI
    x As Long
    y As Long
End Type

this are the declarations
let me write some samples wait a sec...
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eliaslopezgtzCommented:
Private Sub draw_MouseDown(button As Integer, Shift As Integer, x As Single, y As Single)
    If button = vbLeftButton Then draw.FillColor = col1.BackColor
    If button = vbRightButton Then draw.FillColor = col2.BackColor
    Dim m As POINTAPI
    m.x = x / 15
    m.y = y / 15
    p = GetPixel(draw.hdc, m.x, m.y)
    ExtFloodFill draw.hdc, m.x, m.y, p, 1
    draw.Refresh
end sub
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eliaslopezgtzCommented:
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BoyidiotAuthor Commented:
thanx for the advice, I'm gonna make sure though that the write be in black/blue, a dark colour.

'you will either need a little bit of mathematics background'- How much?

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eliaslopezgtzCommented:
or maybe if you want...
http://graphics.lcs.mit.edu/classes/6.837/F00/Lecture04/

best regards and don't forget to accept an answer
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BoyidiotAuthor Commented:
I wont forget, I'm just gonna give it another couple of days or so
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cool12399Commented:
how about giving me the points?? :)
now *theres* good advice!

to do it correctly (make it look good), you will either need a fair amount, or
hire someone skilled to do it. a simple flood fill will not work (will only do adjacent pixels
of the same color).

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eliaslopezgtzCommented:
you are right... help us please
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BoyidiotAuthor Commented:
well I've done it, it just needs abit of tunig to get it perfect, but I DID IT!!!

heres how,

i've got two pictureboxes one with the picture in it. then the user selects a colour, It splits that colour into RGB, then the program gram goes through each pixel(about 10000 a second) and sees if its darker or lighter than the set colour. If it is darker it transfers it to the other picturebox.

well thanx guys
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