The SonarPen was launched through Kickstarter in 2018.  It was primarily designed for iOS and Android smartphones and tablets as a cheap alternative to the expensive styli like the Apple Pencil. 

We actually have been in contact with  SonarPen's creator Elton Leung since 2018.   We were hoping they can add Windows support ever since. To date, there's still no Windows driver but thanks to the support from SpaceDesk, we can now use it for Windows apps too.

SpaceDesk is a software tool that allows a host machine to use other machines like tablets as its monitors.  Their ability to build a monitor wall is amazing. Recently they added support for relaying pen input too, so it's possible to use SpaceDesk as a wireless Pen Display. With SpaceDesk, we're now able to use SonarPen on Windows apps, including our Expresii that features beautiful organic digital watercolor. 

Previously, we tried   Easy Canvas Pro  (US$5 / year) and   SuperDisplay   (US$10 one time)   for Pen-Display application. Currently, we think SuperDisplay  gives the best performance among the three.  SuperDisplay  does support pen tilt, which is quite important for our app Expresii.   SpaceDesk doesn't support pen tilt nor  multi-touch gestures yet. SpaceDesk is currently free to use, while they also offer a Business license. Our current recommendation is still   SuperDisplay, which is the fastest, the most feature-complete and is inexpensive.   We look forward to SuperDisplay supporting the SonarPen.

2021.05.06 Update:  you can use USB tethering for faster connection on SpaceDesk.

What can still be added: ​It'd be great  if any of these programs can relay accelerometer/orientation sensor  readings and act as a G-Sensor  of Windows tablets so that we can directly control paper tilt in Expresii to direct the paint flow. Using other apps like  Sensor stream IMU+GPS  alongside is no good, as only one  app can be in the foreground and nowadays smartphones would have background apps dormant  after a few moments. We've tried putting the app in Battery Saving Exception or disable Battery  Optimization (on Android 9) but to no vain.

In the above video, we also show the new features of  Brush Tilt Control Pad    and   Auto Settle Timer:

You can now stack paint in the same layer by settling paint. We've also added a timer for auto-settling. You can try these new features in a beta version of Expresii, which you can enable by selecting beta option in the System>Advanced tab. Please let us know how you like them.

Expresii user  Steve Kim just sent us a screenshot of Expresii   running on his Apple M1 machine on via Parallels 16.5:

We're amazed that it actually runs fine!

Steve shared: "At  4K screen resolution, I was getting 60 FPS during strokes and around 80 while not stroking. Full screen w/ the default landscape canvas and the largest brush. 1440p was 80 FPS while painting, 120 FPS when not stroking. The VM was set to 6 virtual cores and 8GB of ram on my 16GB M1 Mac Mini running the latest ARM build of Windows 10 via Parallels trial."

The installation process was like documented in the following video:

2022 update: it's running well on M1 Mac Book Air via Parallels Desktop 17. We get 80+ to 50+ FPS on full-screen:

How does a 2020-released HP  laptop convertible perform with Expresii? We had a chance to test   an 13" HP Envy x360 with AMD 4700U APU​. The machine is compact and sleek.  It's so thin that they have the USB-A ports use an expanding door design, which you may find it a bit troublesome to use as you can't simply push a USB head straight into the port but needing to make the door fully open first. Some call a hybrid / convertible a 2-in-1 but note that this HP uses a folding design and the keyboard is not detachable like the Microsoft Surface Pro for it to be truly a thin tablet. 

The HP machine does run hot when if we continuously make strokes for a while. However, the hot part resides in the bottom side near the hinge, which we won't touch normally.  We are pleased by the APU performance, which gives 100+ FPS on the laptop's FHD screen resolution.   Our unit has 8GB of RAM.

 Having tried the RENAISSER   Raphael 520,   the HP tilt Pen feels less sensitive on the initial activation force.  You have to press a bit harder in order for the lines to get registered.  The HP tilt Pen feels solid with its metal body.  The USB type-C charging port is hidden in a sliding door. 

The HP tilt pen doesn't have a   soft tip like found in the Raphael 520 or the MS Surface pen. When used on the glossy screen of the HP machine, it feels slippery. This could be the reason why you see the lines in our tests are wobbly.

Overall, we think the HP Envy x360 is a solid machine, but for better art making, we recommend replacing the included (included at least in our local market) HP tilt pen with cheap  but more sensitive   Surface pen alternatives (they are all compatible under the MPP 2.0 protocol), and you will have a great drawing experience. 

There's also 15" sibling models   if you need a bit larger display. Currently, we don't recommend the Intel integrated GPU models, since there's an issue with Intel GPU artwork exporting, so make sure you pick up the model with an AMD or Nvidia GPU.  There's also newer 2021 models with AMD 5000 series APU announced last month that you can already   buy now .

目前字體設計都是以拉曲線（curve）形式來進行，這裡curve 是指字體的輪廓線（outline），這讓調整效率偏低，如一捺要變窄，則要左右邊的curve 都調整。這是字體設計師許瀚文​  Julius Hui 的示範 ：

雖然 GlyphsApp 有所謂‘Smart Component’ 功能可以先把同一個部件的幾個不同形態設好再interpolate得到中間形態，但始終還是用 outline 來定義，有時interpolate 出來還是有點怪怪的。

筆者覺得這尤其不配合中文書法體的製作：書法字本來就是一筆一筆寫出來，但掃描進電腦也是一大堆curve點，要簡化和一條條曲線調整，筆劃也不能自動分離來方便修改。以下是 Justfont 的示範：

近年有歐洲人提出用 skeleton-based 的辦法，革新傳統的造字系統，這與筆者的想法非常接近：

這樣產生的中文字型，我們當然可以更改筆的粗度、水分、紙材等參數以求不同的效果，但問題是不好嵌入到現在的outline font 系統，因為飛白、墨色變化等東西在傳統的outline font 系統難以表現。筆者跟字體設計師 柯熾堅老師 Sammy Or 前輩談過，他就很喜歡我們的墨色變化呢！

Outline-based  font 有個好處，就是簡單，方便用於像Postscript 那樣的頁面描述語言裏。最初鐳射打印機也配備晶片運行自己的rasterizer，可以直接執行Postscript 指令。現在電腦運算力強，rasterization   都在電腦裡用軟件實現， 打印機則不必自備rasterizer。

而筆者現在的proposal，用虛擬毛筆畫出stroke-based 字型，是基於利用現代電腦的GPU 運算力。現代電腦的GPU在這20年內進步很快，現在即便是 integrated GPU的運算力也追上來了，故筆者認爲是可能的。當然具體軟件工程，仍有待進一步優化實現：因爲目前Expresii 要把字寫每筆出來，有寫的‘過程’，畫出一個字會較慢。日後，可能要開發些parallel 筆劃等的演算法，加快rendering速度，才能配上電腦屏幕顯示和打印的應用。目前Expresii 畫了一個字，只要保留intermediate 結果，其rendering engine 是可以很快得render出不同大小的。所以cache 系統也要考慮，做出優化的新字型系統。如最終不夠快做内文顯示，其實也用於標題字款，反正書法風的字，比較適合標題而非内文。

一般硬筆的藝術性比毛筆差，因為筆觸變化沒那麼大。但現在電子筆透過軟件，藝術性變得媲美甚至超越毛筆。
​
筆者很希望​學校考慮推廣電腦書法教學。我們辦學，是為準備孩子應付未來30年的挑戰。現在電子產品越來越流行，電子書法必然會發展出來的。未來的人會更多時間用電子筆，就像現代人用硬筆多於毛筆一樣。來，讓我們一起參與這場書法革命！

自從西方硬筆傳入東方，我們日常書寫已棄毛筆取硬筆，硬筆之普及也讓我們發展出‘硬筆書法’。​嚴格來說，現在的電子筆是硬筆的一種。試想想，電子產品之應用也越催普及，電腦書法乃必然發展出來。而筆者一直努力深耕，開發書法水墨軟件Expresii，目前已經可寫出比美毛筆書法的作品，毛筆多變之特性比任何其他軟件都好。

電腦書法（中國大陸叫‘數字書法’；台灣叫‘數位書法’）之藝術性是介乎於毛筆跟硬筆之間。數位有硬筆 的方便，但也只有約一毫米的按壓距程，跟真毛筆約一寸有差。

以下是在微軟的Surface Book 2 上書寫示範：

但蔡生覺得筆還不完善，我說硬件方面我無能為力，我只做軟件。他則叮囑我要跟電子筆製造商一起完善電子書法體驗。其實我多年也有接觸硬件商Wacom 給意見，但公司太大，意見是否真的傳達到決策者則不得而知。我也嘗試跟大陸品牌Huion 、友基等聯繫，可惜更難接觸。大概他們都忙於佔領能賺錢的數位板市場，沒空照顧電腦書法。

水墨作品能複製嗎？可以，有榮寶齋的木板水印工藝。雖然這工藝被譽為‘絕活’，但是要人手把原圖分成‘圖層’（所以非所有畫作都能複製），再把圖層雕刻於木板上，再人手於木板上色一板一板的印圖，工序非常複雜。但如果是數位作品，圖層固然有，當然複製或網絡傳送，也可無損​。

宣紙上的墨跡很難修改，所以水墨畫被譽為世上最'真誠'的畫種。但就算名家如徐悲鴻，有時也希望可以修改：榮寶齋曾替​徐悲鴻以 木板水印方法複製一幅奔馬圖，​​徐悲鴻覺得馬腿畫太長了，問可否於複製品中修改呢。在電腦世界，數位作品是可以無縫修改。有修改的能力，你可以不用，但也難否定這能力的用處。

繪畫過程是可以記錄下來，重複演示。這其實對教學很有幫助，因爲東西本身已經是數位格式，要了解過程不需要用攝影機拍著老師作畫。繪畫過程只記錄用筆用墨的數據，檔案也非常小，方便網絡傳送。

電腦的出現，并不代表我們摒棄傳統。為了迎合電腦時代，電子書法的開發，正正是需要我們去耕耘，把傳統延伸到數碼領域。

筆者推廣電子書法時，通常放眼年輕一代，因​老一輩手熟於傳統毛筆，通常會要求電子筆跟傳統毛筆做到一模一樣，但這其實受硬件限制，目前仍難以實現*。目前硬件生產商較着重發展模仿西方硬筆，希望日後硬件商多多跟我們交流合作，一起完善電子書法體驗。

教育部門如認同筆者愚見，也希望也能撥出資源，一起讓電腦書法普及起來！

*  全球最大電子筆生產商Wacom 乃日本公司，日本人當然有想過要電子筆模仿毛筆，但這30年歷史的公司仍未做有效模仿毛筆的電子筆（不是只是把毛束當一個點而已，如   Sensu Brush）出來，可想這不是那麼容易的事情。真筆沾水用在電腦繪畫有LightStrokes，但其還有問題：1.沒有cursor 你要猜下筆位置。2. 濕筆在玻璃上滑動完全不像在紙上寫字般，寫書法的話比較難操控。這些問題仍有待解決。

For those who want to use our paint app Expresii on Mac,  here're some updated tests for you.   

First, we verified that Expresii x64 (version 2021.02.22) artwork saving and snapshot export work correctly on Parallels Desktop 16. However,  we found two issues with pen tilt reading on Parallels Desktop 16 for Mac: 1. Y-tilt is up-side-down. 2. Tilt reading is reported during hovering but not when pen is touching the surface. Pen display is XP-Pen Artist 12 Pro with driver version 2.18 (2021-02-26) on Mac. ​

For comparison, we also ran Expresii in native Windows 10 on the same machine. We get 55-70 FPS on Parallels and 80-95 FPS native Windows 10.  That is, we get about 25-30% performance hit.  Note that the FPS here is our simulation FPS rather than display FPS. The display resolution does affect the performance. The screen resolution is 1920x939 under Parallels, a little less than native FHD 1920x1080 of the pen display on which we ran native Windows 10, so we already gave a little advantage to running under Parallels when we  measure the FPS.

The tilt reading is also correct  out of the box on native Windows 10.  We don't even need to install driver for the pen display before we can the correct tile values via Windows Ink.  As you can see in the video below, we get tilt reading for both pen hovering and touching the surface.  Previously, we have the tilt reading correct on Windows 10 (via Windows Ink or vendor's own wintab32.dll) for various tablet vendors including Wacom, Huion, XP Pen & Microsoft Surface Pen, so we believe we're reading the tilt values correctly from the app. 

Previously, a user sent us a video of Expresii running on Parallels 15. She was using iPad + Apple Pencil for stylus input via Sidecar , and she also got that up-side-down tilt. At that time,  we thought it could be specific to this sidecar setup so we just reversed it back via Expresii's setting (as shown in the above video) for correct control. But now   we get inverted Y-tilt even on XP-Pen , so we believe Parallels should change its way interpreting the value for Windows Ink.

Test system specs:
CPU: i5-8259U
GPU: Iris Graphics 655 (Parallels Intel 14.7.8 driver with OpenGL 3.3)
Pen display: XP-Pen Artist 12 Pro with driver version 2.18 (2021-02-26) on Mac
Virtualization   software:   Parallels Desktop for Mac version 16.2.4 (49160)
OS: MacOS Catalina 10.15.7

We're officially into the second year  of the pandemic.   Time went by so quickly.    In case you didn't notice, over 15% of 2021 already passed.   February 12th marked the start of the Lunar New Year of the   Ox. I used to make some art to celebrate it but this year I did very little. Not because I'm lazy, but because I'm occupied with adding exciting new features to Expresii.

The following is a technology preview that I can show you now. Watch it in 4k to appreciate the vector-like  zooming capability. Yes, Expresii would have pastel.  ​ When most would think there isn't much we can still improve the state of the art, we came up with an efficient method that renders the artwork in extremely high resolution.  R&D (Research & Development) takes time, but it's worth the wait.  I mean, some real R&D, not just recreating what others already did.

With  more and more people get vaccinated, hopefully we'll be able to live a normal life again soon. Stay safe and creative!

Been trying out some apps that turn your tablet/phone into a pen display for your PC.  Thanks to a user, I now come across SuperDisplay. To use Expresii with SuperDsiplay, please use Expresii 2020.12.29 or later. Otherwise, you need to first disable Wintab driver in the current SuperDisplay before you launch Expresii. I've been in contact with the author of SuperDisplay   and and he confirms that future version of SuperDisplay would have this fixed.

Among the similar apps that I've tried, SuperDisplay is the first one that feels a charm to use! It is very fast even on 2.4GHz wifi.   There're many options like having our Android device in extended display mode, customizable on-screen icons (can have different assignment for long press) for undo, redo and more.   Connect wired or wireless. 

The following is a comparison between using my phone as extended display  vs mirrored display at 4k. My computer (AMD 2400G APU with 16GB of RAM) is stressed when it needs to handle two 4k displays causing lag in the strokes, but if you use mirrored mode, it's quite fast:

If you only  use FHD, it should run even smoother.   

Here's a video showing how to setup custom on-screen icons in SuerDisplay and a demo of using them:

The on-screen icons may be  taking too much of your real estate.  However, the above videos are done on the Samsung Note 8 phone.  Want to see how it looks if you use a tablet?  Someone actually has already posted  a demo video of using Expresii with SuperDisplay before me:

He is using a Samsung Tab S4 , a 10.5" Android tablet (2018, Super AMOLED, 1600 x 2560 pixels, 16:10 ratio). As suggested by reviews on Google Play,  another good tablet you can use is the newer Samsung Tab S6 Lite (2020, 10.4"   TFT, 1200 x 2000 pixels, 5:3 ratio), which is sold for US$325 at Amazon. If you're  in Hong Kong, dcfever has several listings at HK$2000 only    (=USD258) right now.  So, yeah, you can pretty much have something like a   wireless Cintiq for 200 or 300 something.

SuperDisplay is current sold at USD10. Well worth the money if you ask me.  ^_^

I tried my Xiaomi Mi A1 (Snapdragon 625, 4+64GB), a budget phone released in 2017. The performance is a bit slower than my Samsung Note 8  (Snapdragon 835, 6+128GB), a flagship phone also from 2017. With more testing, I found that when doing multi-touch gesture (that requires when  fullscreen refresh) would be more laggy if I have more tabs opened in Chrome on my PC. Apparently, the most demanding task SuperDisplay does is the compression of your screen on our PC end and thus the bottomneck.

From Google Play reviews, it looks like the 2019 Samsung Tab A with S Pen works well, and  it's quite a budget device at US$245.

2021.01.09 update:  The author of SuperDisplay told me that for most cases the bottleneck is in the decoder on the Android device. And on your PC, GPU is used for the encoding, so having a fast GPU helps in getting faster response.

2020 went too quickly. No travel. In fact, our activities were mostly confined in our neighborhood.​  Nevertheless, the development of Expresii never stopped. Just check our Update Log for a (truncated) list of what have been done.  

Have been collaborating with a small team of animators this year on a short film Find Find , whose production started in March.  It serves as an experiment for how Expresii can be used for animation. We are developing a system that can automatically control the brush (and other attributes like color loading) in Expresii to produce a sequence of animation frames.  This lays a ground for modern ink-painting animation  (水墨動畫). Click the octopus below to watch an illustrative video.

The animation is set to premiere  in mid-2021.   

In mid-2020, it's been proven that Expresii can run on an Intel-based Mac via Parallels Desktop 15 or later, complete with Apple Pencil support (with pressure and tilt) via Sidecar, but the save / export function of Expresii was not working  due to limitation of Parallels' OpenGL implementation. Since version 2020.11.01, we updated Expresii to overcome this limitation so that it can now run  fully via Parallels. So, yeah, apart from running Expresii via Bootcamp, you can now run it directly from within MacOS via Parallels. 

However, it seems Apple is ditching Intel processors for future Mac's in flavor of their own ARM-based processors. For Expresii to run on ARM,  a crucial part from Microsoft is the support of  OpenGL 3.3+ for Windows on ARM. They have good progress on this, citing   in November   an   Insider version of the compatibility package  that one can test with.  Since one can already   run Windows on ARM on Apple's new M1-based machines, it's quite possible we can run Expresii on ARM-based Apple hardware. 

Those of you having an ARM-based machine can try Windows on ARM (if on Apple M1, here's an   installation guide) and get the   Insider preview     of the OpenGL 3.3 package to try Expresii there already. For those of you hoping to run it via   Parallels,  Parallels just released a   tech preview  in which you can run Windows on ARM as virtual machine  on an M1 Apple machines. So for those of you having a Parallels 16 license, you can already try it.   If you do try them, let me know how it goes!  

2021-04 Update:   Yes, Expresii  runs on Windows 10 ARM version via Parallels 16.5 on Apple Silicon M1 machine!

In March 2020, we got a call from Taiwanese company Ufro.  Their CEO would like us to support their new color-picking mechanism, in preparation for the then-upcoming Lenovo E-Color Pen. We're happy to help. In July this E-Color Pen started to hit the market, and we did some demos for it. Expresii became the only app that can show off this E-Color Pen with gorgeous  color blending effects. 

In May, we added support for on-the-fly adjustment of loading color hue, lightness & saturation via hotkeys in Expresii.   More pen tablet makers are adding dials to their hardware and we also showed you can use those dials for real-time  color adjustment  by assigning the dial to our hotkeys. 

We have been in contact with other hardware makers  too.  Would reveal more when collaborations come to fruition.

Since February, the file size of an Expresii artwork file and in-memory storage size are significantly reduced.   In October, the artwork export rendering implementation is replaced with one that is more amenable to having more layers.  In December, artwork  rendering is also optimized to up to 50% faster (or  80% for a bit lower quality). These path the way  to allowing more layers  or future enhancements. 

Sorry for the lack of a roadmap thus far.   Since the internal of Expresii is much more complex than ordinary paint programs, it takes more effort to design and implement stuffs.  Quite some users still don't have a good GPU and without  a good GPU, we have to be economical when using GPU resources. Now that hardware has improved and capable GPUs are more common in new machines, we'd like to update Expresii to allow better experience given more available GPU compute and memory   resources.

Suminagashi is a form of marbling.  In October, we   gave a preview   of our implementation in Expresii and we passed it to our trusted user Shuen Leung, and she produced the following artwork:

There is still some more work to be done before we can release it to the public. Let us know how you like it so far.

I know many of you find it hard to paint when the paint never really dries and needing to use a new layer for sharp overlapping shapes.   That would change soon. 

With those optimizations mentioned above, we're ready to add support for more layers.

We'll start adding Western watercolor specific features like drips, backruns or granulation.

Some of you were asking for image import.  With that above-mentioned dry-up change, import would be possible.

Our Nelson Chu has been thinking about how to do even better than what he did for oil paint simulation in  Fresh Paint (Project Gustav) . Hopefully, we can come up with a good solution in the coming year following Western watercolor.

We already have an initial implementation of the RYB color model. This makes the colors look more natural, but it actually narrows the range of possible colors you can get. The greys become kind of sepia. 

Existing customers will get these enhancements for free.  So, you don't need to wait if you want to purchase Expresii now.  ​ (^人^)

​If you like what we're doing, please support this endeavor by buying the app (or giving a tip by paying for a trial key) and tell your friends who might be interested.  Everything counts!     Thanks you!      m(_    _)m 

Apart from Duet Display  Pro,  there's also Easy Canvas Pro from DEVGURU Co.  in   Korea that allows you to use your iOS or Android device as pen display to your desktop apps.  Yes, it's like connecting a Cintiq to your desktop, but you have the option to go either wired or wireless.  You can use a tablet like   the iPad or  the   Samsung Tab S3   or even your Samsung Note 10 phone.  It'd be  a great solution if you already own one of those devices.

We just tested  their newly released   EasyCanvas Pro for Android . I own a Samsung Note 8 with S Pen, which supports both pressure and tilt, so I used it in this test.  Normally, you should use a tablet instead since a phone's screen is very small for painting.

I found the wired connection gives satisfactory performance. When using 2.4GHz wifi, the delay is rather noticeable.   Unfortunately, I don't have a 5GHz router here so I can't test 5GHz   performance. The Samsung device shows the 2.4GHz wifi  giving 144Mbps, while my test desktop is connected to the wireless router via cable.  My desktop screen is at 4k and my phone is set at FHD+, so Easy Canvas has to resample the 4k screen capture and that's another source of latency.   

We hope DEVGURU can support G-Sensor data and hover in the future.   G-Sensor can be used for surface tilt to direct the paint flow, and hover is good for users to see the pen posture before hitting the paper. This is important for Eastern calligraphy, if not for painting in general.