When you embark on a project, the first thing a developer ought to do is to run some basic math. Especially if you already have some specs regarding the number and sizes of assets. Because otherwise you may end up trying hard to work around a memory related issue which perhaps even modern desktop computers would struggle with.
So today, I’ll do some math for you, the things you should consider before starting a project or adding one more of those big new shiny features to your app. Kind of like an addendum to my popular article about memory optimization and reducing bundle size.
How much wood texture would a woodchuck choke on if a woodchuck could choke on wood textures?
A texture is an in-memory representation of an image made up of individual pixels. Each pixel uses a certain amount of memory to represent its color. A texture’s memory size is therefore simply the product of width * height * sizeof(color).
Before I go any further, I like to stress it again: the size of an image file is much smaller than the size of the texture generated from the image. Don’t use image file sizes to make memory usage estimations.
Most common are 32-Bit and 16-Bit textures which use 4 and 2 Bytes respectively per pixel. A 4096×4096 image with 32-Bit color depth therefore uses 64 MB memory. Let that sink in for a moment …
At 16-Bit it only uses half of that, though without color dithering (TexturePacker does this for you) this might not look too good depending on the image.
This is pretty much what you’re stuck with unless you export textures as .pvr.ccz. Not only does this format load tremendously faster than PNG (not to speak of JPG which are unbearably slow to load in cocos2d), the .pvr.ccz format also reduces the texture memory size because the texture can stay compressed in memory.
It’s extremely difficult to estimate how much smaller a PVR texture’s memory footprint will be without actually giving it a try. But you can expect anywhere between 10% to 50% reduction.
To the non-power-of-two!
This continues and concludes the previous post of the Fast Pixel-Perfect Collision Detection for Cocos2D with Example Code (1/2) article.
