gdImageRotateInterpolated() converts the source image to truecolor #320
Description
If a palette image is passed to gdImageRotateInterpolated() it is converted to truecolor. That is at the very least unexpected, because gdImageRotateInterpolated() is supposed to return a modified result, but not to change the source image.
Test Program
#include <stdio.h>
#include <assert.h>
#include <gd.h>
int main()
{
gdImagePtr src, dst;
int black;
src = gdImageCreate(10, 10);
black = gdImageColorAllocate(src, 0, 0, 0);
printf("src is truecolor: %d\n", gdImageTrueColor(src));
dst = gdImageRotateInterpolated(src, 30.0, black);
assert(dst != NULL);
printf("src is truecolor: %d\n", gdImageTrueColor(src));
}
Expected Output
src is truecolor: 0
src is truecolor: 0
Actual Output
src is truecolor: 0
src is truecolor: 1