PNG images could be compressed to reduce ELF size slightly

[mark_k]

Hi,

I noticed that the PNG images used in Open PS2 Loader can be made a bit smaller using the PNG optimisation program PNGOUT.

For example, I tried running PNGOUT on the few largest PNG files. Here are the before and after file sizes:

app.png: 6042 -> 5828
config.png 5174 -> 5174 (no improvement)
eth.png 5373 -> 5211
exit.png 4236 -> 4040
hdd.png 7241 -> 6990
logo.png 63906 -> 55319
save.png 2978 -> 2759
usb.png 4905 -> 4803

Because most files are fairly small the optimised versions are only a couple of hundred bytes shorter. But the optimised logo.png is about 8.4KB shorter. The total saving for those PNG files is 9731 bytes. Not a huge difference, but it would speed up loading the OPL ELF file ever so slightly.

I ran all the PNG files through PNGOUT and the result is attached. Total bytes saved: 12897
Update: I tried again with different settings and got the total size down to 105877 bytes (vs 118956 for the originals), saving 13079 bytes.
Update 2: Total size down to 105642 bytes, saving almost exactly 13KB.
Update 3: "Fixed" optimised PNGs zip attached. It turns out OPL can't handle paletted PNGs with transparent colour. It needs all the images to be RGB+alpha.

[fresh]

Hi!

Have you noticed most of the png-optimizers destroy gradients?
Or produce other unacceptable results.

For me it makes no sense to reduce the elf via png optimizers.
Maybe i am wrong. Concrete pro examples for that?


Rgds.

[mark_k]

Well hopefully, the zip I uploaded with the optmised PNGs should be a good example.

Compare them with the original OPL PNGs. They should be pixel-for-pixel 100% identical to the originals. If they're not, please let me know as that would indicate a bug in PNGOUT.

[fresh]

Well hopefully, the zip I uploaded with the optmised PNGs should be a good example.

Compare them with the original OPL PNGs. They should be pixel-for-pixel 100% identical to the originals. If they're not, please let me know as that would indicate a bug in PNGOUT.

Hi!

Okay. I had a quick look at the files.
The sources have been optimized before, so it's difficult to say something about the results.

And, what i said before were my experiences, but one question is still there: Why this?


Rgds.

[mark_k]

Why not? Replacing the current PNGs with optimised ones would be an easy way to reduce the file size slightly, which should make OPL ever-so-slightly quicker to load from memory card.

PNGOUT is supposed to be lossless, so regardless of how the original PNGs in OPL were generated, the output from running them through PNGOUT should be identical in terms of the image content. From what you said, I guess there exist some other PNG optimiser programs which are not lossless; maybe they reduce the size of the palette or something?

[fresh]

Why not? Replacing the current PNGs with optimised ones would be an easy way to reduce the file size slightly, which should make OPL ever-so-slightly quicker to load from memory card.

Hopes and illusions die at last...

The ps2 has a memory bandwidth of ~3.2 gigabytes per second.
The mc makes around 50-100kB per second. That would be 0.1-0.2 seconds faster loading @ 10kB reduction.
Maybe simply load elfs from usb or hdd if the mc is too slow.



Rgds.

[AKuHAK]

There is such a thing called "double packing". I can explain it:
Example:
We have 2 files which are 5Mb and 10Mb. With 7-zip Ultra compression we can archive it both to 1Mb. But if this 2 files firstly pack with zip, we can get sizes, mmmmm...., for example 3Mb un 2Mb. And if we pack this 2 archives with 7-zip ultra compression we get output size 4Mb!!!

According to OPL. With such manipulation we can reduce size of UNPACKED elf but we will increase size of PACKED elf. And the second why we don't use it - for any program is better to reduce unpacking steps for freeing memory.

So, frankly speaking, our purpose is to find all archived data in sources and try to alter it with unpacked (raw) data.

[fresh]

There is such a thing called "double packing". I can explain it:
Example:
We have 2 files which are 5Mb and 10Mb. With 7-zip Ultra compression we can archive it both to 1Mb. But if this 2 files firstly pack with zip, we can get sizes, mmmmm...., for example 3Mb un 2Mb. And if we pack this 2 archives with 7-zip ultra compression we get output size 4Mb!!!

According to OPL. With such manipulation we can reduce size of UNPACKED elf but we will increase size of PACKED elf.

Interesting point.

And the second why we don't use it - for any program is better to reduce unpacking steps for freeing memory.

As i know the ps2-packer stubs use in place unpacking.



Rgds.

[mark_k]

There is such a thing called "double packing". I can explain it:
Example:
We have 2 files which are 5Mb and 10Mb. With 7-zip Ultra compression we can archive it both to 1Mb. But if this 2 files firstly pack with zip, we can get sizes, mmmmm...., for example 3Mb un 2Mb. And if we pack this 2 archives with 7-zip ultra compression we get output size 4Mb!!!

According to OPL. With such manipulation we can reduce size of UNPACKED elf but we will increase size of PACKED elf. And the second why we don't use it - for any program is better to reduce unpacking steps for freeing memory.

So, frankly speaking, our purpose is to find all archived data in sources and try to alter it with unpacked (raw) data.

I understand your example. However, remember that PNG file compression is done with some knowledge of the image structure, whereas the generic zip/7z compression works for arbitrary data.

My guess is, if you were to build an OPL ELF with the optimised PNGs, the final size after ps2packer would be smaller than the original/release OPL ELF.

If you want to try building OPL using uncompressed PNGs, check the archive attached. It contains all the PNGs in OPL uncompressed. For example logo.png expands in size to 405489 bytes uncompressed.

Update: "Fixed" uncompressed PNGs zip attached. It seems OPL doesn't work with paletted PNGs where one palette entry is transparent. It needs RGB + alpha images.

[fresh]

Hi!

My guess is, if you were to build an OPL ELF with the optimised PNGs, the final size after ps2packer would be smaller than the original/release OPL ELF.

Nop. You have not understood AKuHAK's words and the "doubler effect".


Rgds.