refine image scaling behaviourHEADmaster

1 files changed, 28 insertions, 16 deletions

diff --git a/osd.lua b/osd.lua
index f9d4078..36026cb 100644
--- a/osd.lua
+++ b/osd.lua
@@ -184,8 +184,9 @@ function mt:load_img()
 		'magick', self.img.path,
 		'-depth', '8',
 		'-resize', string.format(
-			'x%%[fx:max(%d, min(%d, %d*h/w))]',
-			self.img.min_h, self.img.max_h, self.img.max_w),
+			'x%%[fx:max(min(%d,%d*h/w),min(%d,%d*h/w))]',
+			self.img.min_h, self.img.min_w,
+			self.img.max_h, self.img.max_w),
 		'-print', '%w %h',
 		'tmp.bgra'
 	}
@@ -261,32 +262,42 @@ end
 function mt:set_img(path, menu_res)
 	-- images require *real* dimensions and coordinates, unlike other OSD
 	-- functions which scale the given values automatically
-	local padding = self.scale * self.padding
-	local start = self.scale * menu_res.x1
+	local padding = math.ceil(self.scale * self.padding)
+	local start = math.ceil(self.scale * menu_res.x1)
 	local fs = self.scale * config.font_size
 
 	-- images are scaled to fit the available OSD area when treated as
-	-- having the 2:3 aspect ratio of a standard film poster. when this
-	-- results in an image height less than a minimum font-size-derived
-	-- value, the image is instead scaled to this minimum height. this
-	-- ensures that a given screen has all images, regardless of original
-	-- aspect ratio, scaled to either a common width or a common height.
+	-- having the 2:3 aspect ratio of a standard film poster. a minimum
+	-- size, derived from font size and total area, is used as a fallback
+	-- when insufficient space remains, potentially overlapping the tail
+	-- end of text. when the underlying image reaches this minimum height,
+	-- the 2:3 treatment is abandoned, fixing the height and allowing the
+	-- image to grow horizontally to an arbitrary limit, after which the
+	-- width becomes fixed and the height continues to shrink.
+	--
+	-- this is designed to keep images legible while fixing at least one
+	-- dimension under normal circumstances, preventing jarring switches
+	-- between different images rendered on the same menu.
 	--
 	-- because we have only the total width of the current OSD text, we
 	-- cannot slightly reduce the image width to avoid overlapping some
 	-- longer line at the bottom, as we do not know where the offending
 	-- line is. if it were possible to place images *under* text, maybe
 	-- we'd allow overlap, but mpv currently hard-codes this order.
-	local min_h = math.floor(3 * fs)
-	local max_h = math.floor(math.max(min_h, math.min(
-		self.height - 2*padding,
-		(self.width - start - 2*padding) * 3/2)))
-	local max_w = math.floor(max_h * 2/3)
-	local top = math.floor(padding)
-	local right = math.floor(self.width - padding)
+	local pw = self.width - 2*padding
+	local min_h = math.min(3 * fs, pw * 3/2)
+	local min_w = math.ceil(math.min(3 * min_h, pw))
+	local max_h = math.max(min_h, math.min(
+		self.height - 2*padding, (pw - start) * 3/2))
+	local max_w = math.ceil(max_h * 2/3)
+	min_h = math.floor(min_h)
+	max_h = math.floor(max_h)
+	local top = padding
+	local right = self.width - padding
 
 	if self.img and path == self.img.path and
 			min_h == self.img.min_h and
+			min_w == self.img.min_w and
 			max_h == self.img.max_h and
 			max_w == self.img.max_w then
 		if top == self.img.top and right == self.img.right then
@@ -305,6 +316,7 @@ function mt:set_img(path, menu_res)
 	self.img = {
 		path = path,
 		min_h = min_h,
+		min_w = min_w,
 		max_h = max_h,
 		max_w = max_w,
 		top = top,