Micropython jpegdec::get_width()/get_height() will always return 0

[Skyler84]

Due to the // Just-in-time open of the filename/buffer, get_width and get_height will always return 0 as the jpeg is never actually loaded when these functions are called. This means the user cannot check the size of the jpeg and change the x/y/scale when decoding it based on the size.

This should probably be fixed by loading the jpeg at the time of calling open_file() or open_RAM(), which would also want a close() function.

[Gadgetoid]

You're right- PNGDEC rectifies this (and avoids the need for close) by opening the file to grab the width/height and store it on the Python object instance-

pimoroni-pico/micropython/modules/pngdec/pngdec.cpp

Lines 292 to 321 in bff2453

	mp_obj_t _PNG_openFILE(mp_obj_t self_in, mp_obj_t filename) {
	_PNG_obj_t *self = MP_OBJ_TO_PTR2(self_in, _PNG_obj_t);
	// TODO Check for valid filename, and maybe that file exists?
	self->file = filename;
	pngdec_open_helper(self);
	self->width = self->png->getWidth();
	self->height = self->png->getHeight();
	self->png->close();
	return mp_const_true;
	}
	// open_RAM
	mp_obj_t _PNG_openRAM(mp_obj_t self_in, mp_obj_t buffer) {
	_PNG_obj_t *self = MP_OBJ_TO_PTR2(self_in, _PNG_obj_t);
	// TODO Check for valid buffer
	self->file = buffer;
	pngdec_open_helper(self);
	self->width = self->png->getWidth();
	self->height = self->png->getHeight();
	self->png->close();
	return mp_const_true;
	}

This pattern was never backported to JPEGDEC, but probably should be.

[Skyler84]

I've changed #895 to backport the PNGDEC fix, adding width/height to the _JPEG_obj_t and setting those on open(), creating a helper function jpegdec_open_helper(self) and using that in the open functions and decode. I've also reverted my previous changes so it's just the backport (the MP close() binding is removed etc)

[Skyler84]

fixed by #899