热成像调色板

Posted 2023-03-29

【中文标题】热成像调色板

【英文标题】：Thermal imaging palette

【发布时间】：2015-04-14 05:54:57

【问题描述】：

自热成像早期以来，红外热像仪通常使用从黑色到蓝色、品红色、橙色、黄色到亮白色的独特调色板。这个调色板通常被称为 Iron 或 Ironbow。

这是使用前视红外相机拍摄的图像的典型假色可视化（来源：***）。

"Termografia kot" by Lcamtuf - 典型的伪彩色红外线

在一个专门的红外图像论坛上，我发现了一个 2005 年的帖子，其中包含一个离散的调色板，似乎与我正在寻找的内容很接近。

来源不明的离散 FLIR 调色板

但是，与彩虹调色板一样，最好有一个简洁的分析表达式来定义调色板。

对于使用过 GNUPLOT 的人来说，这个调色板可能看起来很熟悉，因为默认的 PM3D 调色板运行 black-blue-magenta-orange-yellow。

GNUPLOT PM3D 调色板

这个调色板有一个简洁的定义

r = Math.round(255*Math.sqrt(x)); 
g = Math.round(255*Math.pow(x,3)); 
b = Math.round(255*(Math.sin(2 * Math.PI * x)>=0?
                   Math.sin(2 * Math.PI * x) : 0 ));

但是，其他调色板的外观并不完全如此。对我的口味来说有点太褐色了。有关 FLIR 相机中使用的调色板的来源或分析表达式的任何其他信息都会有所帮助。

我创建了一个JSFiddle 来使用不同的调色板。

【问题讨论】：

我希望these graphs 帮助:-) 肯定有一个简洁的公式，但我还没有弄清楚。

【参考方案1】：

您不太可能找到调色板的公式。所以你应该使用一个颜色数组。

这是 FLIR 的 Iron 调色板（来自 here），它的颜色在一个数组中：

var iron_palette = ["#00000a","#000014","#00001e","#000025","#00002a","#00002e","#000032","#000036","#00003a","#00003e","#000042","#000046","#00004a","#00004f","#000052","#010055","#010057","#020059","#02005c","#03005e","#040061","#040063","#050065","#060067","#070069","#08006b","#09006e","#0a0070","#0b0073","#0c0074","#0d0075","#0d0076","#0e0077","#100078","#120079","#13007b","#15007c","#17007d","#19007e","#1b0080","#1c0081","#1e0083","#200084","#220085","#240086","#260087","#280089","#2a0089","#2c008a","#2e008b","#30008c","#32008d","#34008e","#36008e","#38008f","#390090","#3b0091","#3c0092","#3e0093","#3f0093","#410094","#420095","#440095","#450096","#470096","#490096","#4a0096","#4c0097","#4e0097","#4f0097","#510097","#520098","#540098","#560098","#580099","#5a0099","#5c0099","#5d009a","#5f009a","#61009b","#63009b","#64009b","#66009b","#68009b","#6a009b","#6c009c","#6d009c","#6f009c","#70009c","#71009d","#73009d","#75009d","#77009d","#78009d","#7a009d","#7c009d","#7e009d","#7f009d","#81009d","#83009d","#84009d","#86009d","#87009d","#89009d","#8a009d","#8b009d","#8d009d","#8f009c","#91009c","#93009c","#95009c","#96009b","#98009b","#99009b","#9b009b","#9c009b","#9d009b","#9f009b","#a0009b","#a2009b","#a3009b","#a4009b","#a6009a","#a7009a","#a8009a","#a90099","#aa0099","#ab0099","#ad0099","#ae0198","#af0198","#b00198","#b00198","#b10197","#b20197","#b30196","#b40296","#b50295","#b60295","#b70395","#b80395","#b90495","#ba0495","#ba0494","#bb0593","#bc0593","#bd0593","#be0692","#bf0692","#bf0692","#c00791","#c00791","#c10890","#c10990","#c20a8f","#c30a8e","#c30b8e","#c40c8d","#c50c8c","#c60d8b","#c60e8a","#c70f89","#c81088","#c91187","#ca1286","#ca1385","#cb1385","#cb1484","#cc1582","#cd1681","#ce1780","#ce187e","#cf187c","#cf197b","#d01a79","#d11b78","#d11c76","#d21c75","#d21d74","#d31e72","#d32071","#d4216f","#d4226e","#d5236b","#d52469","#d62567","#d72665","#d82764","#d82862","#d92a60","#da2b5e","#da2c5c","#db2e5a","#db2f57","#dc2f54","#dd3051","#dd314e","#de324a","#de3347","#df3444","#df3541","#df363d","#e0373a","#e03837","#e03933","#e13a30","#e23b2d","#e23c2a","#e33d26","#e33e23","#e43f20","#e4411d","#e4421c","#e5431b","#e54419","#e54518","#e64616","#e74715","#e74814","#e74913","#e84a12","#e84c10","#e84c0f","#e94d0e","#e94d0d","#ea4e0c","#ea4f0c","#eb500b","#eb510a","#eb520a","#eb5309","#ec5409","#ec5608","#ec5708","#ec5808","#ed5907","#ed5a07","#ed5b06","#ee5c06","#ee5c05","#ee5d05","#ee5e05","#ef5f04","#ef6004","#ef6104","#ef6204","#f06303","#f06403","#f06503","#f16603","#f16603","#f16703","#f16803","#f16902","#f16a02","#f16b02","#f16b02","#f26c01","#f26d01","#f26e01","#f36f01","#f37001","#f37101","#f37201","#f47300","#f47400","#f47500","#f47600","#f47700","#f47800","#f47a00","#f57b00","#f57c00","#f57e00","#f57f00","#f68000","#f68100","#f68200","#f78300","#f78400","#f78500","#f78600","#f88700","#f88800","#f88800","#f88900","#f88a00","#f88b00","#f88c00","#f98d00","#f98d00","#f98e00","#f98f00","#f99000","#f99100","#f99200","#f99300","#fa9400","#fa9500","#fa9600","#fb9800","#fb9900","#fb9a00","#fb9c00","#fc9d00","#fc9f00","#fca000","#fca100","#fda200","#fda300","#fda400","#fda600","#fda700","#fda800","#fdaa00","#fdab00","#fdac00","#fdad00","#fdae00","#feaf00","#feb000","#feb100","#feb200","#feb300","#feb400","#feb500","#feb600","#feb800","#feb900","#feb900","#feba00","#febb00","#febc00","#febd00","#febe00","#fec000","#fec100","#fec200","#fec300","#fec400","#fec500","#fec600","#fec700","#fec800","#fec901","#feca01","#feca01","#fecb01","#fecc02","#fecd02","#fece03","#fecf04","#fecf04","#fed005","#fed106","#fed308","#fed409","#fed50a","#fed60a","#fed70b","#fed80c","#fed90d","#ffda0e","#ffda0e","#ffdb10","#ffdc12","#ffdc14","#ffdd16","#ffde19","#ffde1b","#ffdf1e","#ffe020","#ffe122","#ffe224","#ffe226","#ffe328","#ffe42b","#ffe42e","#ffe531","#ffe635","#ffe638","#ffe73c","#ffe83f","#ffe943","#ffea46","#ffeb49","#ffeb4d","#ffec50","#ffed54","#ffee57","#ffee5b","#ffee5f","#ffef63","#ffef67","#fff06a","#fff06e","#fff172","#fff177","#fff17b","#fff280","#fff285","#fff28a","#fff38e","#fff492","#fff496","#fff49a","#fff59e","#fff5a2","#fff5a6","#fff6aa","#fff6af","#fff7b3","#fff7b6","#fff8ba","#fff8bd","#fff8c1","#fff8c4","#fff9c7","#fff9ca","#fff9cd","#fffad1","#fffad4","#fffbd8","#fffcdb","#fffcdf","#fffde2","#fffde5","#fffde8","#fffeeb","#fffeee","#fffef1","#fffef4","#fffff6"];

【讨论】：

数组中有 433 种颜色？我们当然可以做得更好。

如果太多，可以减小数组大小。如果还不够，您可以对缺失值进行插值。如果您有更好的解决方案，我很乐意阅读。

仍在搜索 :-) 到目前为止，我只找到了 120 种色调的索引列表 here

我自己使用问题中显示的图像生成了列表。如果你愿意，我会发布我的脚本。您可以通过首先调整图像大小来设置所需的阴影数量（让您的图像处理软件为您处理插值），然后在该图像上运行脚本。

【参考方案2】：

这些调色板是任意的，主要用于根据您拥有的图像类型提高对比度。因此，这些值可以是纯自定义设置。

由于 IR 不捕获任何颜色（因为它在颜色范围之外），因此返回的亮度值仅映射到创建最佳对比度的值，尤其是在边缘和形状方面。

铁调色板有 5-7 种关键颜色，然后进行插值（红色可以微调黄色和洋红色之间的混合）。确切的值和位置可以任意设置，这里是一个例子：

var ctx = document.querySelector("canvas").getContext("2d");
var gr = ctx.createLinearGradient(0, 0, 600, 0);
var keys = ["white", "gold", "#c07", "#20008c", "black"];

// add color stops to gradient:
for(var i = 0, key; key = keys[i]; i++) 
  gr.addColorStop(i / (keys.length-1), key);


ctx.fillStyle = gr;
ctx.fillRect(0, 0, 600, 20);

<canvas width=600></canvas>