You can check if a file is has a certain format by reading the first few bytes.
FLTK does that for jpeg and all other image files. Take a look at the source of
Fl.jpeg.Image.
If you want to know if a jpeg image is in RGB, you need to read tje entire jpeg
header. Again, FLTK does that using libjpeg. You can see how it's done in the
same source code.
-Matthias
Sent from my relatively smart phone.
jseb <gmane2...@finiderire.com> schrieb:
>Hello,
>
>I wonder how i could detect RGB image format, without loading image in
>a
>buffer, and then parsing its header.
>
>For the moment, i'm doing this in my classe, which is far from being
>efficient:
>
>
>Fl_Image * Images::load (std::string filename)
>{
> Fl_Image *image = is_image_already_loaded(filename);
>
> if (!image) {
> image = new Fl_JPEG_Image (filename.c_str());
> if (image->w()) {
> //the image is cached when loading once.
> liste.insert(std::pair<std::string, Fl_Image *>(filename,image) );
> } else {
> delete image;
> image = 0;
> }
> }
>
> if (!image) {
> image = new Fl_PNG_Image (filename.c_str());
> if (image->w()) {
> liste.insert(std::pair<std::string, Fl_Image *>(filename,image) );
> } else {
> delete image;
> image = 0;
> }
> }
>
> if (!image) {
> image = new Fl_BMP_Image (filename.c_str());
> if (image->w()) {
> liste.insert(std::pair<std::string, Fl_Image *>(filename,image) );
> } else {
> CRITICAL ("unknwown format for : %s\n",filename.c_str());
> delete image;
> image = 0;
> }
> }
>
> return image;
>}
>
>Of course, i could preload the image in a buffer, and then trying
>Fl_JPEG/PNG/BMP_Image from this buffer.
>I could also use a template for the three almost identical load.
>As i cache the picture once loaded, i think i don't get a big speed
>penalty, even if i load BMP pictures.
>
>Thank you.
>(«premature optimizing is the root of all evil», i know too :) )
>
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