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SPDocument * Inkscape::Extension::Plugin::GimpGrad::open ( Inkscape::Extension::Input *  module,
gchar const *  filename 
) [virtual]

Actually open the gradient and turn it into an SPDocument.

Parameters:
module The input module being used
filename The filename of the gradient to be opened
Returns:
A Document with the gradient in it.
GIMP gradients are pretty simple (atleast the newer format, this function does not handle the old one yet). They start out with the like "GIMP Gradient", then name it, and tell how many entries there are. This function currently ignores the name and the number of entries just reading until it fails.

The other small piece of trickery here is that GIMP gradients define a left possition, right possition and middle possition. SVG gradients have no middle possition in them. In order to handle this case the left and right colors are averaged in a linear manner and the middle possition is used for that color.

That is another point, the GIMP gradients support many different types of gradients -- linear being the most simple. This plugin assumes that they are all linear. Most GIMP gradients are done this way, but it is possible to encounter more complex ones -- which won't be handled correctly.

The one optimization that this plugin makes that if the right side of the previous segment is the same color as the left side of the current segment, then the second one is dropped. This is often done in GIMP gradients and they are not necissary in SVG.

What this function does is build up an SVG document with a single linear gradient in it with all the stops of the colors in the GIMP gradient that is passed in. This document is then turned into a document using the sp_document_from_mem. That is then returned to Inkscape.

Reimplemented from Inkscape::Extension::Implementation::Implementation.

Definition at line 137 of file gimpgrad.cpp.

References ColorRGBA::average().

{
    FILE * gradient;
    // std::cout << "Open filename: " << filename << std::endl;

    Inkscape::IO::dump_fopen_call(filename, "I");
    gradient = Inkscape::IO::fopen_utf8name(filename, "r");
    if (gradient == NULL) return NULL;

    char tempstr[1024];
    if (fgets(tempstr, 1024, gradient) == 0) {
        // std::cout << "Seems that the read failed" << std::endl;
        fclose(gradient);
        return NULL;
    }

    if (!strcmp(tempstr, "GIMP Gradient")) {
        // std::cout << "This doesn't appear to be a GIMP gradient" << std::endl;
        fclose(gradient);
        return NULL;
    }

    if (fgets(tempstr, 1024, gradient) == 0) {
        // std::cout << "Seems that the second read failed" << std::endl;
        fclose(gradient);
        return NULL;
    }

    if (fgets(tempstr, 1024, gradient) == 0) {
        // std::cout << "Seems that the third read failed" << std::endl;
        fclose(gradient);
        return NULL;
    }

    ColorRGBA last_color(-1.0, -1.0, -1.0, -1.0);
    float lastlocation = -1.0;
    Glib::ustring outsvg("<svg><defs><linearGradient>\n");
    while (fgets(tempstr, 1024, gradient) != 0) {
        float left, middle, right;
        float temp_color[4];
        int type;
        int color;
        gchar * end;

        left = g_ascii_strtod(tempstr, &end);
        middle = g_ascii_strtod(end, &end);
        right = g_ascii_strtod(end, &end);

        for (int i = 0; i < 4; i++) {
            temp_color[i] = g_ascii_strtod(end, &end);
        }
        ColorRGBA leftcolor(temp_color[0], temp_color[1], temp_color[2], temp_color[3]);

        for (int i = 0; i < 4; i++) {
            temp_color[i] = g_ascii_strtod(end, &end);
        }
        ColorRGBA rightcolor(temp_color[0], temp_color[1], temp_color[2], temp_color[3]);

        sscanf(end, "%d %d", &type, &color);

        if (!(last_color == leftcolor) || left != lastlocation) {
            outsvg += new_stop(leftcolor, left);
        }
        outsvg += new_stop(leftcolor.average(rightcolor), middle);
        outsvg += new_stop(rightcolor, right);

        last_color = rightcolor;
        lastlocation = right;
    }

    outsvg += "</linearGradient></defs></svg>";

    // std::cout << "SVG Output: " << outsvg << std::endl;

    fclose(gradient);

    return sp_document_new_from_mem(outsvg.c_str(), outsvg.length(), TRUE, TRUE);
}


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