PNG may be lossless in theory, but it isn't a certainty. From Wikipedia:
I'm sorry Mike but you're way off in the weeds here. I'm only responding because I'm concerned that if someone follows this advice they will end up there as well.
The most critical thing to remember is that we're talking about
rocket decals here, not scans of the Mona Lisa for the archives.
The PNG working group designed the format for transferring images on the Internet, not for professional-quality print graphics, therefore non-RGB color spaces such as CMYK are not supported. I don't know about you, buy my HP printer uses CMY inks, so PNG is NOT ideal for printing.
Oy.
Your printer (and mine) uses CMYK inks, but the print drivers are designed to accept RGB input and produce accurate printout. There is a much greater than 99% chance that your digital camera is capturing images in RGB.
CMYK workflows are possible, and are generally used for commercial printing, but require higher-end tools (e.g. Photoshop). Mark Hayes prints in CMYK: if you're designing graphics for him to print, you can benefit by starting with CMYK because you'll get a more accurate impression of how things are going to look when printed. But it has nothing to do with compression.
Although PNG is a lossless format, PNG encoders can preprocess image data in a lossy fashion to improve PNG compression. I interpret this to mean that unless you know what compression your program is using, you really can't be sure.
Find me a PNG that you can distinguish from the original. I'll wait.
For all practical purposes for typical use, PNG is lossless.
Below is a screen shot of the same graphic saved as BMP, PNG, JPG and PDF. Bitmaps are the true resolution, pixel for pixel. PDFs, PNG and JPG all crush the bejeezus out of the file. BMP (or RAW if you take a picture with a camera) are you only true sources of lossless graphics. If your source to begin with is PDF, it's already compressed.
View attachment 462391
That means next to nothing. PDF can encapsulate images in different ways. The interceptor decal sheet referenced in this thread is a pure vector image, so even at a tiny 120 KB it provides perfect fidelity at any size.
For certain types of images (which would frequently include the sorts of things you see in rocket decals), the LZ algorithm used in PNG can provide enormous compression ratios with no data loss. PNG works much less well with continuous-tone photographs. It's fidelity will still be fine, it just won't compress very well.
JPEG is almost always lossy and generates artifacts, particularly around sharp edges, which makes it less well suited to text and that sort of thing. But I could easily tweak the JPEG encoder settings to produce an image that, on a rocket, you would not be able to distinguish from uncompressed original, at least not without a loupe.
Bottom line advice:
1) If you can do what you need with a vector graphics tool (e.g. Inkscape), that's great. You'll get fantastic results at any print size.
2) Otherwise, do your bitmap work at a high DPI (I typically use 300), and store files in a lossless format. PNG is great. If you want to use BMP, that's fine too, you're just needlessly burning disk space and slinging around huge files.
3) If you're working with a commercial printer, you may want to look into CMYK workflow, but most don't need to worry about this.
4) Don't use MS Office tools as image editors (sorry, had to include that one
)
