I managed to sort my issue with regards to signing my apk and updating an older CJS google play store listing.
I also get the blurry image issue even on small images. I have to set the high DPI to yes to make smooth graphics for my app. I believe this will give a performance issue on most phones though In CJS all my graphics were fine with that turned off.
—, Mayfly, I managed to set up the test case to reproduce the blurry image issue, and work out a solution to resolve it for Crosswalk.
As mentioned by Mayfly, the image would NOT become blurry if the high DPI is turned on by Contruct2. That is true because, on a high dpi device, the display density is always greater than 1, for example, it is 2.0 on Google Nexus 7, and so window.devicePixelRatio in Crosswalk engine is also set to 2.0. The value of window.devicePixelRatio will be used to draw canvas by C2 runtime if high dpi mode is turned on, to get a more sharp image. In case of high dpi mode is turned off, C2 runtime tries to draw the canvas with the default value 1.0 on a high-dpi screen, as a result, the final image output becomes blurry since the pixels drawn by C2 runtime would be hard-scaled to fit the high-dpi screen dimension.
The solution for Crosswalk is simple, you can pass --force-device-scale-factor=1.0 command line option to Crosswalk engine in assets/xwalk-command-line. Note the command line file is supported from Crosswalk 6.
With the above command line option, the Crosswalk engine force to set the device scale factor to 1.0, and so window.devicePixelRatio is 1.0 accordingly no matter the value of the device density. In this case, when C2 runtime would draw the canvas which can fit the screen dimension without hard-scaled.
The memory consumption is decided by the size of canvas. In case of high dpi mode is enabled, for example, on Nexus7 with 1920x1200 resolution, the canvas size is 1920x1080, while in case of high dpi mode is disabled, the canvas size is 960x540.
Another way to resolve this issue is to enable high dpi mode in C2. Don't worry, it won't consume more memory than CJS. The reason is, CJS has its own implementation for canvas, it internally enables high dpi mode for canvas drawing on a high dpi device regardless of whether it is enabled in Contruct2 project setting.