gnuplot：如何使用像素图显示透明png-解网

问：

我正在尝试使用命令将图像（png）放置在地图顶部。set pixmap

它确实有效，但 png 的透明度没有被“显示”，我得到了一个白色背景。

该功能是否可以处理图像的透明度属性？pixmap

脚本如下：

$DATA<<EOD
1,"Washington",630.2000,1591.1800
EOD
$DATA01<<EOD
1 "C:\\Temp\\Images\\colors.png" 630.2000 1591.1800
EOD
set datafile separator comma
set style data point
set term windows enhanced size 3000.00,2000.00
unset xtics; unset ytics; unset x2tics; unset y2tics
set grid noxtics
set grid noytics
set border 0
set colorsequence classic
set key off
set for [i=1:1] pixmap i word($DATA01[i], 2) center at word($DATA01[i], 3), word($DATA01[i], 4) width 100 height 100 
plot 'C:\Magic\XPA\46s\Add_On\ChartGenerator\Geography\USA_Curved_Names_Blue.png.jpg' binary filetype=JPG w rgbimage,\
$DATA every ::0::0 using ($3):($4) notitle,\
$DATA using ($3):($4):($2) with labels font "Tahoma,20" textcolor rgb "purple" center offset 0,1 notitle

这是PNG文件：

和映射文件：

罗伯托

GnuPlot 透明度像素图

diff -urp original.identify redo.identify 
--- original.identify   2023-10-25 22:38:42.002322272 -0700
+++ redo.identify       2023-10-25 22:38:57.165582322 -0700
@@ -1,5 +1,5 @@
 Image:
-  Filename: original.png
+  Filename: redo.png
   Permissions: rw-r--r--
   Format: PNG (Portable Network Graphics)
   Mime type: image/png
@@ -703,25 +703,26 @@ Image:
   Compression: Zip
   Orientation: Undefined
   Properties:
-    date:create: 2023-10-26T02:58:38+00:00
-    date:modify: 2023-10-26T02:58:34+00:00
-    date:timestamp: 2023-10-26T06:23:13+00:00
+    date:create: 2023-10-26T06:22:24+00:00
+    date:modify: 2023-10-26T06:22:24+00:00
+    date:timestamp: 2023-10-26T06:23:23+00:00
+    png:bKGD: chunk was found (see Background color, above)
     png:IHDR.bit-depth-orig: 8
     png:IHDR.bit_depth: 8
-    png:IHDR.color-type-orig: 2
-    png:IHDR.color_type: 2 (Truecolor)
+    png:IHDR.color-type-orig: 6
+    png:IHDR.color_type: 6 (RGBA)
     png:IHDR.interlace_method: 0 (Not interlaced)
     png:IHDR.width,height: 512, 512
     png:pHYs: x_res=3780, y_res=3780, units=1
-    png:tRNS: chunk was found
+    png:tIME: 2023-10-26T06:22:24Z
     signature: cb4667f54b948708bd7fd893e4668ca843bf816392a4bad8c8917b967cf1f1ea
   Artifacts:
     verbose: true
   Tainted: False
-  Filesize: 11772B
+  Filesize: 11446B
   Number pixels: 262144
   Pixel cache type: Memory
-  Pixels per second: 21.2189MP
+  Pixels per second: 21.0638MP
   User time: 0.010u
   Elapsed time: 0:01.012
   Version: ImageMagick 7.1.1-11 Q16-HDRI x86_64 21206 https://imagemagick.org

如果您在那里发现任何相关内容，请告诉我。如果它是一个可以测试的可重现文件属性，也许可以教 gnuplot 修复它或至少发出警告。

OP 的 PNG 中的所有白色像素都转换为全透明。
一些有意的白色像素也将转换为完全透明
没有部分透明度
原始图像（512x512 像素）的缩放/纵横比显然取决于图形 x，y 范围。因此，您必须修复范围，自动缩放会弄乱您的图表。此外，您需要摆弄缩放因子。

脚本：

### pixmap/rgbalpha transparency
reset session

FILE  = "SO77361444.png"
FILE2 = "SO77361444_inkscape.png"

set xrange[-10:10]
set yrange[0:3]
set key noautotitle
set samples 500

set pixmap 1 FILE  at -8,1 width 4
set pixmap 2 FILE2 at -2,1 width 4
set label 1 at -6,0.75 "OP's original PNG\nas pixmap" center
set label 2 at  0,0.75 "OP's PNG im-/exported\nvia Inkscape\nas pixmap" center
set label 3 at  6,0.75 "OP's original PNG\nas binary w rgbalpha\nand white-->transparent" center

plot for [i=10:30] i/10., \
     FILE binary filetype=png dx=0.0075 dy=0.002 \
       origin=(4,1) u (r=$1):(g=$2):(b=$3):(r*g*b==255**3?0:255) w rgbalpha
### end of script

结果：

gnuplot：如何使用像素图显示透明png

gnuplot: How to display transparent png with pixmap

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