Re: [GD-DEVEL] Need som help writing raw data to a jpg

Hello Tomas,

On 11/8/06, Tomas Zajc <[email protected]> wrote:

> I'm just starting using libgd and I wold need some help. I'm trying to make a
> program that should be able to write some raw data I've got on a float
> pointer to a jpg file. I couldn't find the correct way to do it looking at
> the examples on the gd page.
>
> so long I got
>
>         im = gdImageCreate(outsamples, outlines);
>         black = gdImageColorAllocate(im, 0, 0, 0);
>         white = gdImageColorAllocate(im, 255, 255, 255);
>
>         if((quick=fopen(argv[2], "wb"))==NULL)
>         {
>                 printf("No se pudo abrir el jpg archivo de salida %s\n", argv[2]);
>                 return 2;
>         }
>         gdImageJpeg(im, quick, 70);
>
> but I cant put my data into the im pointer. I I'm not sure which function
> should I use to do it. I tried: gdImageCreateFromJpegPtr(int size, void
> *data) withpout any help.
>
> I'm now starting to doubt if gd can do such thing.
>
>  Any sugestion?

If you target format, I suggest you to use gdImageCreateTrueColor.
This format has "unlimited" colors. The question is what represent the
float values. For the example here, I will suppose you get a two
dimensional array and assign the float value to each channel, red,
green and blue.

im = gdImageCreateTrueColor(outsamples, outlines);
for (y = 0; y < outlines; y++) {
    for (x  = 0; x < outsamples; x++) {
        gdImageSetPixel(im, gdTrueColor(val,val,val));
    }
}
/* Save the image */

gdTrueColor function simply creates the 24bit RGB value (no alpha used
here) using the float value. gdImageSetPixel put this value at the
position (x,y) in the image buffer.

I hope I answered your question, please feel free to ask further
informations or optimizations.

--Pierre