On 07.12.2010, at 23:39, Slick Dealer wrote:
>> On 07.12.2010, at 19:26, Slick Dealer wrote:
>>
>>> If I could easily resize PNG images using FLTK, I wouldn't be using
>>> Fl_Help_View.
>>
>> You can, but it's a low quality resizing algorithm. The key is
>> Fl_Image::copy(int w, int h). You should load the original image
>> and keep it in the background, then use copy() from the original
>> image whenever you need to resize the image to a different size.
>> Don't forget to delete the previous image copy.
>>
>> This works well as long as the quality is high enough for your
>> use case.
>>
>> Albrecht
>
> Albrecht,
> I think I tested Fl_Image resizing but realized that image rendering is much
> better if I use Fl_Help_View to display/resize the image. Has anyone had a
> similar experience?
Image scaling - not perfect but fast and better than just copy(w, h) because it
does at least a little bit of filtering:
/**
* Scale horizontally by 50%.
*/
void Flmp_Image::half_width()
{
if (!w() || !h() || !d() || !array) return;
uncache();
int dw = w()/2, dh = h(), dd = d(), i, j, k, stride = ld();
if (stride==0) stride = w()*d();
uchar *new_array = new uchar[dw*dh*dd];
uchar *dst = new_array;
for (i=0; i<dh; i++) {
const uchar *src = array + i*stride;
for (j=0; j<dw; j++) {
for (k=0; k<dd; k++) {
unsigned short a = src[0];
unsigned short b = src[dd];
*dst++ = (a+b)>>1;
src++;
}
src+=dd;
}
}
if (alloc_array) delete[] (uchar *)array;
array = new_array;
alloc_array = 1;
ld(0);
d(dd);
w(dw);
h(dh);
}
/**
* Scale horizontally by 50%.
*/
void Flmp_Image::half_height()
{
if (!w() || !h() || !d() || !array) return;
uncache();
int dw = w(), dh = h()/2, dd = d(), i, j, k, stride = ld();
if (stride==0) stride = w()*d();
uchar *new_array = new uchar[dw*dh*dd];
uchar *dst = new_array;
for (i=0; i<dh; i++) {
const uchar *src = array + 2*i*stride;
for (j=0; j<dw; j++) {
for (k=0; k<dd; k++) {
unsigned short a = src[0];
unsigned short b = src[stride];
*dst++ = (a+b)>>1;
src++;
}
}
}
if (alloc_array) delete[] (uchar *)array;
array = new_array;
alloc_array = 1;
ld(0);
d(dd);
w(dw);
h(dh);
}
Fl_Image *Flmp_Image::scale(int W, int H) {
if (2*W<w() || 2*H<h()) {
Flmp_Image *img = (Flmp_Image*)copy();
while (2*W<img->w())
img->half_width();
while (2*H<img->h())
img->half_height();
Fl_Image *ret = img->copy(W, H);
delete img;
return ret;
}
return copy(W, H);
}
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