C / C++ / MFC

27-Apr-06 0:05

Hi again i have a strange question to ask i'am not sure if it is applicable but if there is a way to do it here is right place to find out.

i'm working on the implementation of a spam filter and i'm trying to implement a function that extracts the fonts color and the background color from an html file.
What i'm trying to do is check if the font color and the background color are similar (invisible text, common in spam emails) i get the bgcolor and font color in hexadecimal format and i was wondering if there is a class to compare the colors. i found something similar but for c#.net is

System.Drawing.Color cfg = System.Drawing.ColorTranslator.FromHtml(foreColor);

if (cbg.R <= cfg.R + 15 ||cbg.R >= cfg.R - 15)
{
if (cbg.R <= cfg.R + 15 ||cbg.R >= cfg.R - 15)
{
if (cbg.R <= cfg.R + 15 ||cbg.R >= cfg.R - 15)
{
return fsi;
}
}
}
Any ideas
Thanks in advance

Cedric Moonen27-Apr-06 0:14

Cedric Moonen

27-Apr-06 0:14

antonaras_marcou wrote:
i get the bgcolor and font color in hexadecimal format

You mean in a string ? Or how is this value stored ?
Anyway, you can simply compare the strings or the values to check if they are the same or not.

antonaras_marcou27-Apr-06 0:23

27-Apr-06 0:23

Thanks for the reply cedric Moonen

i store the the colors which are in this form #CC0000, #EA0000, #5E5EFF
the problem is that i can't just compare if they are the same because most of the times they use simmilar colors for the bg and fonts but not identical for example white bg and very light yellow for the fonts still unreadable but it won't match if i compare the colors

Stephen Hewitt27-Apr-06 0:51

Stephen Hewitt

27-Apr-06 0:51

There are many way of doing this. One way is to consider the colour as a point in 3D space: The difference between two colours using this scheme is the length of the line between them which we can calculate using Pythagoras’ theorem (extended to 3D).

double Difference(BYTE red1, BYTE green1, BYTE blue1, BYTE red2, BYTE green2, BYTE blue2)
{
    BYTE rdiff = red2-red1;
    BYTE gdiff = green2-green1;
    BYTE bdiff = blue2-blue1;
    return sqrt(rdiff*rdiff + gdiff*gdiff + bdiff*bdiff);
}

The return value will always be positive and you'll have to decide how small a return value means the colours are too close.

Steve

antonaras_marcou27-Apr-06 2:49

27-Apr-06 2:49

This is way to advance for me but i like it looks good i'll try it
Thank very much appresiate the help
i'll post a msg if i need some assistant
thanks again u ve been very helpful

BadKarma27-Apr-06 5:11

BadKarma

27-Apr-06 5:11

Hi,

I don't think this works with bytes suppose the color black (0,0,0) and white (255, 255, 255)
look add the difference of a component say red:

BYTE rdiff = 0 - 255; // rdiff == 1

but when the two colors are almost the same gray (128,128,128) & (127,127,127)

BYTE rdiff = 128 - 127; // rdiff == 1

One must use signed short to let this work.
The multiplication wil create positive numbers

double Difference(short red1, short green1, short blue1, short red2, short green2, short blue2)
{
    short rdiff = red2-red1;
    short gdiff = green2-green1;
    short bdiff = blue2-blue1;
    return sqrt(rdiff*rdiff + gdiff*gdiff + bdiff*bdiff);
}

A good site for this kind of problems is http://www.webwhirlers.com/colors/combining.asp[^]

codito ergo sum

antonaras_marcou27-Apr-06 8:07

27-Apr-06 8:07

Thanks badkarma for the help i think i got it
1.first i need to transform hex to decimal?(do you know how btw Smile | :)

)
2.First 2hex digits corespond to red second 2digits to green and 2 last to blue
3. i perform the arithmetic operations of your function and i set a number (by trial and error to find the compinations of colors that i should consider similar)

looks good thanks again!

if you know any fuction to convert hex to decimal that would be very helpful
Thanks again

Stephen Hewitt27-Apr-06 13:54

Stephen Hewitt

27-Apr-06 13:54

Yes, you right: You'll need to use a signed type as you've done.

Steve

problem in triggering events

David Crow27-Apr-06 3:10

David Crow

27-Apr-06 3:10

antonaras_marcou wrote:
What i'm trying to do is check if the font color and the background color are similar

Similar but not exact?

antonaras_marcou wrote:
i found something similar but for c#.net is

So are you wanting a C++ slution or a C# slution?

antonaras_marcou wrote:
if (cbg.R <= cfg.R + 15 ||cbg.R >= cfg.R - 15)
{
if (cbg.R <= cfg.R + 15 ||cbg.R >= cfg.R - 15)
{
if (cbg.R <= cfg.R + 15 ||cbg.R >= cfg.R - 15)

These three tests appear to do the same thing? Is that intentional?

"Let us be thankful for the fools. But for them the rest of us could not succeed." - Mark Twain

"We will be known forever by the tracks we leave." - Native American Proverb

rajeev8227-Apr-06 0:00

rajeev82

27-Apr-06 0:00

Hi all,
i've developed a dialog based application, which has to respond for certain events (ex:when the sound filled in a buffer has stopped playing.. etc).
To achieve this i've used the function,

MsgWaitForMultipleObjects( 1, &g_hNotificationEvent,FALSE, INFINITE, QS_ALLEVENTS );
where,
g_hNotificationEvent --> handle to the event to be triggered.

the problem what i'm facing is,where to place this function? if i put this within OnInitDialog the application stops executing further.The problem will be solved if this function is placed within
WinMain() ,but where i do i find WinMain in a dialog based MFC application?
It'll be really great if someone can help me out in this.
Thanks and regards,
rajeev

Cedric Moonen27-Apr-06 0:12

Cedric Moonen

27-Apr-06 0:12

Start a separate thread to check for that, otherwise your GUI will freeze until you receive the event.
Once the event is received in your thread, send a user defined message to your dialog to specify that the event is finished.

Roger Stoltz27-Apr-06 0:34

Roger Stoltz

27-Apr-06 0:34

Umm.. The whole thing about having an event signaled is the use of multiple threads.
Since you seem to have only one thread I don't understand why you consider this solution.

Why don't you post a user defined message from where you are signalling the event and write a message handler for that message instead?

--
Roger

It's suppose to be hard, otherwise anybody could do it!

rajeev8227-Apr-06 0:54

rajeev82

27-Apr-06 0:54

Let me explain the application more clearly. i've a demodulator hardware which keeps pumping out some sound data which is being feed to a sound card.
I've used "DirectX" to achieve this. when the sound fed to the card has finished playing ,the application has to be notified so that it can fill the buffer with new data and play it again.This process has to repeat continuously.
Please let me know whether using MsgWaitForMultipleObjects(...)is a good idea ?

rajeev

-- modified at 6:54 Thursday 27th April, 2006

Roger Stoltz27-Apr-06 1:00

Roger Stoltz

27-Apr-06 1:00

rajeev82 wrote:
MsgWaitForMultipleObjects(...)is a good idea ?

It depends on how you know when your demodulator has finished feeding the sound card...

If it signals an event, then I suggest you create a worker thread simply waits for the event with WaitFormUltipleObjects(), presumably there's no need to process messages.

If a message gets posted you write a message handler and restart the feeding process from there.

To be able to help you futher we need to know how you can tell when the demodulator has finished feeding the sound card.

--
Roger

It's suppose to be hard, otherwise anybody could do it!

rajeev8227-Apr-06 1:19

rajeev82

27-Apr-06 1:19

The demodulator doesnt feed the data to the sound card directly.Itz my program which collects the data from the demodulator and feeds it to the sound card so that it can be heard.the sound which comes out from the demodulator is in chunks of 4096 points.
In directx there is a interface called IDirectSoundNotify which will notify my application when one chunk of 4096 has been played ,so that the next 4096 points can be loaded ,played and so on.
as long my application runs the demodulator will work and it'll pump out something(atleast noise).so please tell me how to call a function according to the notification i receive.
rajeev