#
# v-emu-ivbs.awk - emulate IrfanView blur / sharpen effect
#   by uratan! 2021.5.15
#
	#
	# generates convolution-matrix for pnmconvol
	# you can emulate IrfanView's effect by:
	#  +-------------------------------------------------------
	#  |M="sharpen"; P=30; F="matrix.PGM"		# blur or sharpen
	#  |
	#  |echo "$M $P $F" | awk -f v-emu-ivbs.awk
	#  |djpeg src.jpg | pnmconvol $F | cjpeg -q 85 > tuned.jpg
	#  |rm  $F
	#  +-------------------------------------------------------
	#
	# CAUTION:
	#  [1] convolution-matrix is on PGM format but it is not pure PGM image,
	#      see manual page of pnmconvol for detail.
	#  [2] some rounding errors are still remained...
	#       (IrfanView: truncate  vs  pnmconvol: rounding,  maybe...)
	#  [3] "the edge of the image is not converted. simply copied"
	#      is same by both pnmconvol and IrfanView, maybe...
	#
{
	method = $1;		# "blur" or "sharpen"
	p      = $2;		# effect settings from 1 to 99
	name   = $3;		# name of matrix file

	if(method == "blur") {
	#
	# blur
	#   f = 0.0 +     p / 800;		[0, 0.125]
	#   e = 1.0 - 8 * p / 800;		[0, 1.0]
	#
		#name = sprintf("mat_b%02d.PGM", p);
		bias = 800;
		maxv = 2 * bias;
		f = (bias)            + p;
		e = (bias) + bias - 8 * p;

		print  "P2"                      > name;
		print  "3 3"                     > name;
		print  maxv                      > name;
		printf("%3d %3d %3d\n", f, f, f) > name;
		printf("%3d %3d %3d\n", f, e, f) > name;
		printf("%3d %3d %3d\n", f, f, f) > name;
	} else {
	#
	# sharpen
	#   f = 0.0 -     p / 200;		[-0.5, 0]
	#   e = 1.0 + 8 * p / 200;		[   1, 5]
	#
		#name = sprintf("mat_s%02d.PGM", p);
		bias = 200;
		maxv = 2 * bias;
		f = (bias)            - p;
		e = (bias) + bias + 8 * p;

		print  "P2"                      > name;
		print  "3 3"                     > name;
		print  maxv                      > name;
		printf("%3d %3d %3d\n", f, f, f) > name;
		printf("%3d %3d %3d\n", f, e, f) > name;
		printf("%3d %3d %3d\n", f, f, f) > name;
	}
}