Make image scaling more efficient by using an image cache and recording whether an image has been shrunk

1 files changed, 26 insertions, 12 deletions

diff --git a/tkread b/tkread
index e6c7c87..9b8cc6c 100755
--- a/tkread
+++ b/tkread
@@ -78,6 +78,9 @@ set replacements { \
 	{{\\_} "_"} \
 }
 
+array set imgcache {}
+array set imgshrunk {}
+
 if { $::argc > 0 && [lindex $::argv 0] == "-h" } {
 	puts "Usage: $usage"
 	exit
@@ -122,6 +125,8 @@ proc markup {widget} {
 	global tagnum
 	global underlinenum
 	global prefixnum
+	global imgcache
+	global imgshrunk
 
 	# process replacements
 	foreach item $replacements {
@@ -164,6 +169,9 @@ proc markup {widget} {
 		set localfile [file tail $src]
 		if [file exists $localfile] {
 			set curimg [image create photo -file $localfile]
+			set imgcache($curimg) [image create photo]
+			$imgcache($curimg) copy $curimg
+			set imgshrunk($curimg) 0
 			$widget image create $insertion -image $curimg -align baseline
 			set cur $insertion
 		} else {
@@ -307,6 +315,7 @@ proc changeFontSize {change} {
 	global underlinenum
 	global prefixfmt
 	global prefixnum
+
 	set newsize [expr $fontsize $change]
 	if {$newsize > 0} {
 		set fontsize $newsize
@@ -331,20 +340,27 @@ proc changeFontSize {change} {
 }
 
 proc reduceImageIfNeeded {img maxwidth} {
+	global imgshrunk
+
 	set curwidth [image width $img]
 	if {$curwidth > $maxwidth} {
-		set t [image create photo]
-		$t copy $img
-		$img blank
-		set zoom [expr round($curwidth.0 / $maxwidth)]
-		$img copy $t -shrink -subsample $zoom
-		image delete $t
+		set zoom [expr int(ceil($curwidth.0 / $maxwidth))]
+		if {$zoom > 1} {
+			set t [image create photo]
+			$t copy $img
+			$img blank
+			$img copy $t -shrink -subsample $zoom
+			image delete $t
+			set imgshrunk($img) 1
+		}
 	}
 }
 
 proc scaleImages {} {
 	global fontfamily
 	global fontsize
+	global imgcache
+	global imgshrunk
 
 	foreach img [.t image names] {
 		# note width is 64 * (width of '0' char)
@@ -352,12 +368,10 @@ proc scaleImages {} {
 		set maxwidth [expr $charwidth * 64]
 		set curwidth [image width $img]
 		if {$curwidth < $maxwidth} {
-			# re-load the image as it may have been shrunk
-			# TODO: could make this more efficient by keeping track of which images actually have been shrunk
-			# TODO: also should keep copies of the original image in memory
-			puts "$curwidth < $maxwidth"
-			set f [$img cget -file]
-			$img read $f
+			if { $imgshrunk($img) == 1 } {
+				$img copy $imgcache($img)
+				set imgshrunk($img) 0
+			}
 		}
 		reduceImageIfNeeded $img $maxwidth
 	}