reading TIFF mono files fails

[bradh]

heif-enc with a single band file fails with an error like:

Could not encode HEIF/AVIF file: Encoder plugin generated an error: Unsupported bit depth: Bit depth not supported by x265

The error is misleading though. Its really an invalid pixel image being passed as input. That happens because of this logic:

libheif/examples/decoder_tiff.cc

Lines 307 to 321 in 8cc6c79

	struct heif_image* image = nullptr;
	heif_colorspace colorspace = bpp == 1 ? heif_colorspace_monochrome : heif_colorspace_RGB;
	heif_chroma chroma = bpp == 1 ? heif_chroma_monochrome : heif_chroma_interleaved_RGB;
	if (bpp == 4) {
	chroma = heif_chroma_interleaved_RGBA;
	}
	err = heif_image_create((int) width, (int) height, colorspace, chroma, &image);
	(void) err;
	// TODO: handle error
	switch (config) {
	case PLANARCONFIG_CONTIG:
	{
	heif_channel channel = heif_channel_interleaved;

(and equivalent call for the planar case).

Essentially we're creating a mono image, then adding an interleaved image plane, which doesn't make sense.

I'm currently working on a fix.

[bradh]

This is resolved via the way #1301 got pulled in.