icat: Allow controlling how images are fit

Fixes #9201

docs/changelog.rst

@@ -139,13 +139,17 @@ Detailed list of changes
 
 - Add support for the `paste events protocol <https://rockorager.dev/misc/bracketed-paste-mime/>`__ (:iss:`9183`)
 
+- icat kitten: Add support for animated PNG and animated WebP, netPBM images, ICC color profiles and CCIP metadata to the builtin engine
+
+- icat kitten: Add a new flag :option:`kitty +kitten icat --fit` to control how images are scaled to fit the screen (:iss:`9201`)
+
+- icat kitten: The :option:`kitty +kitten icat --scale-up` flag now takes effect when not using :option:`kitty +kitten icat --place` as well
+
 - Add a mappable action :ac:`copy_last_command_output` to copy the output of the last
   command to the clipboard (:pull:`9185`)
 
 - ssh kitten: Fix a bug where automatic login was not working (:iss:`9187`)
 
-- icat kitten: Add support for animated PNG and animated WebP, netPBM images, ICC color profiles and CCIP metadata to the builtin engine
-
 - Graphics: Fix overwrite composition mode for animation frames not being honored
 
 - Automatic color scheme switching: Fix title bar and scroll bar colors not being updated (:iss:`9167`)

kittens/icat/main.go

@@ -42,6 +42,15 @@ const (
 	supported
 )
 
+type fit_t int
+
+const (
+	fit_none fit_t = iota
+	fit_width
+	fit_height
+	fit_both
+)
+
 var transfer_by_file, transfer_by_memory transfer_mode
 
 var files_channel chan input_arg
@@ -49,6 +58,7 @@ var output_channel chan *image_data
 var num_of_items int
 var keep_going *atomic.Bool
 var screen_size *unix.Winsize
+var fit_mode fit_t
 
 func send_output(imgd *image_data) {
 	output_channel <- imgd
@@ -87,6 +97,22 @@ func parse_z_index() (err error) {
 	return
 }
 
+func parse_fit() (err error) {
+	switch strings.ToLower(opts.Fit) {
+	case "width":
+		fit_mode = fit_width
+	case "height":
+		fit_mode = fit_height
+	case "none", "neither":
+		fit_mode = fit_none
+	case "both":
+		fit_mode = fit_both
+	default:
+		return fmt.Errorf("unknown fit specification: %#v", opts.Fit)
+	}
+	return nil
+}
+
 func parse_place() (err error) {
 	if opts.Place == "" {
 		return nil
@@ -130,8 +156,10 @@ func print_error(format string, args ...any) {
 
 func main(cmd *cli.Command, o *Options, args []string) (rc int, err error) {
 	opts = o
-	err = parse_place()
+	if err = parse_place(); err != nil {
-	if err != nil {
+		return 1, err
+	}
+	if err = parse_fit(); err != nil {
 		return 1, err
 	}
 	err = parse_z_index()

kittens/icat/main.py

@@ -22,9 +22,16 @@ be positioned at the top left corner of the image, instead of on the line after
 
 --scale-up
 type=bool-set
-When used in combination with :option:`--place` it will cause images that are
+Cause images that are smaller than the specified area to be scaled up to use as much
-smaller than the specified area to be scaled up to use as much of the specified
+of the specified area as possible. The specified area depends on either the :option:`--place`
-area as possible.
+or the :option:`--fit` options.
+
+
+--fit
+choices=width,height,both,none
+default=width
+When not using :option:`--place`, control how the image is scaled relative to the screen.
+You can have it fit in the screen width or height or both or neither.
 
 
 --background

kittens/icat/native.go

@@ -91,12 +91,37 @@ func add_frame(ctx *images.Context, imgd *image_data, img image.Image, left, top
 	return &f
 }
 
+func scale_up(width, height, maxWidth, maxHeight int) (newWidth, newHeight int) {
+	if width == 0 || height == 0 {
+		return 0, 0
+	}
+
+	// Calculate the ratio to scale the width and the ratio to scale the height.
+	// We use floating-point division for precision.
+	widthRatio := float64(maxWidth) / float64(width)
+	heightRatio := float64(maxHeight) / float64(height)
+
+	// To preserve the aspect ratio and fit within the limits, we must use the
+	// smaller of the two scaling ratios.
+	var ratio float64
+	if widthRatio < heightRatio {
+		ratio = widthRatio
+	} else {
+		ratio = heightRatio
+	}
+
+	// Calculate the new dimensions and convert them back to uints.
+	newWidth = int(float64(width) * ratio)
+	newHeight = int(float64(height) * ratio)
+
+	return newWidth, newHeight
+}
+
 func scale_image(imgd *image_data) bool {
 	if imgd.needs_scaling {
 		width, height := imgd.canvas_width, imgd.canvas_height
-		if imgd.canvas_width < imgd.available_width && opts.ScaleUp && place != nil {
+		if opts.ScaleUp && (imgd.canvas_width < imgd.available_width || imgd.canvas_height < imgd.available_height) && (imgd.available_height != inf || imgd.available_width != inf) {
-			r := float64(imgd.available_width) / float64(imgd.canvas_width)
+			imgd.canvas_width, imgd.canvas_height = scale_up(imgd.canvas_width, imgd.canvas_height, imgd.available_width, imgd.available_height)
-			imgd.canvas_width, imgd.canvas_height = imgd.available_width, int(r*float64(imgd.canvas_height))
 		}
 		neww, newh := images.FitImage(imgd.canvas_width, imgd.canvas_height, imgd.available_width, imgd.available_height)
 		imgd.needs_scaling = false

kittens/icat/process_images.go

@@ -8,6 +8,7 @@ import (
 	"image"
 	"io"
 	"io/fs"
+	"math"
 	"net/http"
 	"net/url"
 	"os"
@@ -196,15 +197,29 @@ type image_data struct {
 	source_name string
 }
 
+const inf = math.MaxInt
+
 func set_basic_metadata(imgd *image_data) {
 	if imgd.frames == nil {
 		imgd.frames = make([]*image_frame, 0, 32)
 	}
-	imgd.available_width = int(screen_size.Xpixel)
-	imgd.available_height = 10 * imgd.canvas_height
 	if place != nil {
 		imgd.available_width = place.width * int(screen_size.Xpixel) / int(screen_size.Col)
 		imgd.available_height = place.height * int(screen_size.Ypixel) / int(screen_size.Row)
+	} else {
+		switch fit_mode {
+		case fit_none:
+			imgd.available_width, imgd.available_height = inf, inf
+		case fit_both:
+			imgd.available_width = int(screen_size.Xpixel)
+			imgd.available_height = int(screen_size.Ypixel)
+		case fit_width:
+			imgd.available_width = int(screen_size.Xpixel)
+			imgd.available_height = inf
+		case fit_height:
+			imgd.available_width = inf
+			imgd.available_height = int(screen_size.Ypixel)
+		}
 	}
 	imgd.needs_scaling = imgd.canvas_width > imgd.available_width || imgd.canvas_height > imgd.available_height || opts.ScaleUp
 	imgd.needs_conversion = imgd.needs_scaling || remove_alpha != nil || flip || flop || imgd.format_uppercase != "PNG"

kittens/icat/scaling_test.go

@@ -0,0 +1,29 @@
+package icat
+
+import (
+	"fmt"
+	"image"
+	"testing"
+)
+
+var _ = fmt.Print
+
+func TestScaling(t *testing.T) {
+	for _, tc := range []struct {
+		w, h, pw, ph, ew, eh int
+	}{
+		{1000, 50, 800, 600, 800, 40},
+		{1000, 50, 800000, 600, 12000, 600},
+		{100, 50, 800, 600, 800, 400},
+		{1920, 1080, 800, 600, 800, 450},
+		{300, 900, 800, 600, 200, 600},
+		{400, 300, 800, 600, 800, 600},
+	} {
+		aw, ah := scale_up(tc.w, tc.h, tc.pw, tc.ph)
+		actual := image.Pt(aw, ah)
+		expected := image.Pt(tc.ew, tc.eh)
+		if actual != expected {
+			t.Fatalf("want: %v got: %v", expected, actual)
+		}
+	}
+}