Re: [GD-DEVEL] trasparent image width antialiasing

----- Original Message ----- 
From: "yagyog" <[email protected]>
To: "Pierre" <[email protected]>
Cc: <[email protected]>
Sent: Thursday, February 01, 2007 5:06 PM
Subject: Re: [GD-DEVEL] trasparent image width antialiasing


> ----- Original Message ----- 
> From: "Pierre" <[email protected]>
> To: "yagyog" <[email protected]>
> Cc: <[email protected]>
> Sent: Thursday, February 01, 2007 4:04 PM
> Subject: Re: [GD-DEVEL] trasparent image width antialiasing
> [cut]
>>> >
>>> > These images are not correct. There is no alpha used in the text and
>>> > the green/red "backgournd "colors are still used.
>>> >
>>> > You have to create images _without_ background color and only use
>>> > _alpha_ for the text anti aliasing.
>>> >
>>> >> my result
>>> >> http://www.yag.altervista.org/varius/1/test.png
>>> >
>>> > Yes, and it is expected, you have green and red artifacts.
>>> >
>>> And this
>>> http://www.yag.altervista.org/varius/1/T1.png
>>
>> Yes, this one is correct.
>
> well therefore with an image of this type as I can make? I add: and if my 
> image instead is flat but with the witnesses with antialing I cannot just 
> make nothing?
I try this code

int
remove_background(gdImagePtr im1, int color1, int color2, gdImagePtr 
im2,gdImagePtr im_out)
{
 float alpha=0.0;
 int alphaBlend,pxTemp;
 int x, y,fx,fy,btl, btr, bbl, bbr;
 int alphaColor,calcAlpha;

alphaBlend = 100;

 for(int i=0;i<(gdImageSX(im1));i++)
    for(int j=0;j<(gdImageSY(im1));j++)
    {
        //alphaBlend= gdAlphaBlend (color2,pxTemp);
        alphaColor = gdTrueColorAlpha(
                     gdTrueColorGetRed(pxTemp),
                     gdTrueColorGetGreen(pxTemp),
                     gdTrueColorGetBlue(pxTemp),
                     calcAlpha
                     );

        alphaColor = alphaBlend * gdImageGetTrueColorPixel (im1, i, j) + 
(1 - alphaBlend) *     gdImageGetTrueColorPixel (im2, i, j);
        gdImageSetPixel (im_out, i, j, alphaColor);

    }
 gdImageColorTransparent (im_out, color1);
 gdImageSaveAlpha (im_out, 1);
 mySavePng ("test.png", im_out);

 return 1;
}

the formula is:
http://en.wikipedia.org/wiki/Alpha_blending

tnks