gdImageSetStyle() and gdImageLine() instead of gdImageDashedLine()

dashed_line.c

#include <string.h>
#include <gd.h>


/* does not try to create a symmetric pattern */
void dashed_line(gdImagePtr im, int x1, int y1, int x2, int y2, int color)
{
    int wid = im->thick; /* this may have to be adjusted */
    int *oldStyle, oldStyleLength = im->styleLength, oldStylePos = im->stylePos;
    int *newStyle, newStyleLength = wid * gdDashSize * 2;
    int i;

    oldStyle = malloc(oldStyleLength * sizeof(int)); /* should actually be gdMalloc() */
    memcpy(oldStyle, im->style, oldStyleLength * sizeof(int));

    newStyle = malloc(newStyleLength * sizeof(int)); /* should actually be gdMalloc() */
    for (i = 0; i < newStyleLength; i++) {
        newStyle[i] = (i < newStyleLength / 2 ? color : gdTransparent);
    }
    gdImageSetStyle(im, newStyle, newStyleLength);
    gdImageLine(im, x1, y1, x2, y2, gdStyled);

    free(newStyle); /* should actually be gdFree() */
    memcpy(im->style, oldStyle, oldStyleLength * sizeof(int));
    im->styleLength = oldStyleLength;
    im->stylePos = oldStylePos;
    free(oldStyle); /* should actually be gdFree() */
}


int main()
{
    gdImagePtr im;
    FILE *fp;

    im = gdImageCreateTrueColor(100, 100);
    gdImageFilledRectangle(im, 0, 0, 99, 99, 0xffffff);
    gdImageSetThickness(im, 3);
    dashed_line(im, 10, 10, 90, 80, 0x000000);
    gdImageDashedLine(im, 10, 20, 90, 90, 0x000000);
    fp = fopen("dashed_line.png", "wb");
    gdImagePng(im, fp);
    fclose(fp);
    return 0;
}