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  1.  
    I don't know what's going on. I've tried to post my latest Black Talon Reach WIP, but every time I try, the post doesn't go through, and I get sent to a 'start a new discussion'. I don't understand what's going on... anyone else having any troubles?
    • CommentAuthorLorelei
    • CommentTimeAug 1st 2016
     
    I was a few moments ago, as well, trying to post an image of Tempest Shrine for Mark to see....i ended up trying 5 times until it finally went through!
  2.  
    I finally got it.. thanks!
    • CommentAuthorJimP
    • CommentTimeAug 1st 2016
     
    Size restrictions here. I think 800 pixels wide is it.
    •  
      CommentAuthorDogtag
    • CommentTimeAug 1st 2016 edited
     
    People have consistently been posting images wider than the requested 800 pixels, so it's more likely a file size issue. I think I read that someone had trouble with files over 2 MB. But that's just an educated guess.
    • CommentAuthorLoopysue
    • CommentTimeAug 1st 2016
     
    The sticky note from Ralph says 1024kb, but most of the City maps I've uploaded have been slightly over that limit, so I think the info may be out of date?

    Even though the mapping community doesn't seem to like JPGs all that much, you can upload a much higher resolution level in JPG than PNG, because the file size itself is smaller than a PNG at the same resolution.
    • CommentAuthorJimP
    • CommentTimeAug 1st 2016
     
    I use Irfanview to lower the color depth, that decreases, sometimes by 50 percent, a file's size.
    • CommentAuthorLoopysue
    • CommentTimeAug 1st 2016
     
    By that do you mean using a colour palette, rather than full colour?

    I hadn't thought of that, but even if you didn't mean using a colour palette, I can see all kinds of possibilities now that you've triggered the thought. Why - you could upload images at twice the resolution, providing you didn't mind any subtle graduations being a bit stripy, but in most maps that isn't a problem because there's already so much going in with the textures anyway.
    • CommentAuthorJimP
    • CommentTimeAug 1st 2016 edited
     
    Its a menu selection in Irfanview under the Image menu at the top of the program. I tried several numbers to see what would still show a good image on my site n several browsers, and also reduce file size.
      decrease_depth.png
    • CommentAuthorLoopysue
    • CommentTimeAug 1st 2016 edited
     
    @Jim - That's a colour palette. We were talking about the same thing.

    The image that you would create with that particular set up would only have 202 different colours in it as opposed to the 65536 in a typical non-paletted PNG (24 bit colour).

    Interestingly, the only difference between Irfanview and my very outdated CorelDraw is that I have more optimisation choices (the three tick boxes at the bottom). Different methods of optimisation = different methods of blending just 2 colours to create the 3 or 4 shades between them.

    @ Storm - I'm not so sure this technique of reducing the number of colours (and therefore the file size) would work as well for more colourful maps, but it might be worth a try if you've done something with a relatively limited range of colours in it.
    • CommentAuthorJimP
    • CommentTimeAug 1st 2016
     
    Hmmm... To me a colour pallette is the colors themselves. The Amiga computer I had back about 1980, used 'color depth' to mean maximum number of possible colors. More depth, more possible colors. So its called a color pallette now. I'm a bit confused, but I'll learn.
    • CommentAuthorLoopysue
    • CommentTimeAug 1st 2016
     
    Every image has a palette, which consists of all the colours in that image. With a typical 24 bit colour image there are a possible 65536 different shades. Not all images make use of all those 65536 colours, and black and white images may only use about 50 or so shades of grey, but however many an image actually holds is its individual and actual 'palette'.

    What our software can do is reduce the memory required to save that image by switching it from the 24 bit colour system down to its own palette, but the snag is that any such 'paletted image' may only have a maximum of 256 colours. To make up for the missing colours the software works out how blend the ones in the palette to generate the appearance of other colours that had to be deleted just to get the image down to 256 colours from however many it had before.

    The way it does this is usually some form of dithering, which is adding different proportions of pixels of one colour into another to visually create a third colour that is no longer present in the new 256 limited palette. In the old days paletted images used to look spotty because of the relatively low resolutions, but now its pretty hard to tell unless you enlarge the image until the pixels are visible as individual dots.

    As an extreme example of this process - if you reduced the palette of a photograph of oranges in a big red and yellow fruit bowl down to just 5 colours or so, you might find that the only orange colouring in the fruit itself would consist entirely of different mixtures of red and yellow dots.

    There are a range of different procedures for deciding a) which colours to keep, and b) how to dither the remaining colours together to regenerate those which are now missing. That is why you have three tick box options at the bottom of your dialogue.

    I'm sorry Jim. I'm not really all that good at explaining things like this. Maybe, if you're lucky Remy will be able to sum it up in that marvellously efficient way he has that always makes me wish I was half as eloquent! LOL
    • CommentAuthorjslayton
    • CommentTimeAug 1st 2016
     
    Technical notes:
    typical JPEG = 24-bit images (8 bits each of red, green, and blue) with lossy compression and no transparency.
    typical 24-bit PNG = 24-bit images (8 bits each of red, green, and blue) with lossless compression and optional 8-bit transparency.
    typical 8-bit PNG = up to 8-bit color palette, lossless compression, optional chroma-keyed transparency (one color in the palette is designated as transparent)
    GIF = up to 8-bit color palette, lossless compression, optional chroma-keyed transparency (one color in the palette is designated as transparent)

    Common meanings of "bits" in relation to graphics files
    8 bits = 2^8 or 256 possible items
    16 bits = 2^16 or 65536 possible items. for color images, the 16 bits often encodes 5:5:5:1 RGBA bits or 5:6:5:0 RGBA bits in the most popular formats
    24 bits = 2^24 or 16777216 possible items. for color images, the 24 bits usually encode 8:8:8 RGB bits.
    32 bits = 2^32 or 4294967296 possible items. for color images, the 32 bits usually encode 8:8:8:8 RGBA bits, but may encode 10:10:10:2 RGBA or 10:12:10:0 RGB bits for certain formats.
    48 bits = 2^48 or 281474976710656 possible items. for color images, the 48 bits usually encode 16:16:16:0 RGBA bits, but various formats may include 8 or 16 bit alpha channels. Note that in some cases, the format of those 16 bits is not a linear numeric value from 0 to 65535, but encodes a low-precision floating-point format for HDR usage.

    For paletted file formats, the palette is typically represented by a set of 24-bit RGB values. The individual pixels in the file represent an index into the palette information. A palette typically has between 2^1 and 2^8 entries, giving 2 to 256 possible colors. One color is often sacrificed to represent a transparent color. The small number of physical colors may be perceptually expanded by use of dithering, or representing colors that would take a large number of bits as groups of colors that take a smaller number of bits, but spreading out those smaller colors over a spatial extent to represent the original data. Dithering is typically ordered (the pattern of pixels used to represent other colors is fixed) or an error diffusion algorithm such as Floyd-Steinberg (the error between the encoder's internal understanding of what the color ought to be and what colors it can represent is spread out over nearby pixels an a semi-random way that is less visually distracting than an ordered dither often is). Dithering is often less efficient in terms of storage space required because encoders require regular patterns to conserve space: an error-diffusion dithering scheme may double or triple the size of a file compared to an ordered dither, which may be larger in turn than no dithering at all.

    Paletted graphics hardware such as the original EGA and VGA systems used a 4-bit (EGA) or 8-bit (VGA) memory subsystem to represent each pixel. As each pixel was read from memory, it was used as a lookup into a hardware table of RGB values (6:6:6 RGB for 262144 possible colors). Most graphics hardware these days uses RGB pixel representation and paletted displays have fallen out of favor because of the relative cheapness of memory compared to the earlier hardware systems. Paletted image file formats, however, remain popular because they can often give better visual fidelity for a given number of bits than other approaches.

    The Amiga was an interesting system because it was possible to reprogram the palette lookup table to any of the possible 4096 colors at each scan line, making it possible to show the full 4096 colors over the course of the whole screen refresh, but only 32 on any given line. Ah, the bad old days... Not as bad as the Apple 2 high-res encoding, but bad!
    • CommentAuthorLoopysue
    • CommentTimeAug 1st 2016
     
    Thanks Joe. That just about covers anything anyone would ever want to know about all the different kinds of rendered image. I couldn't help but smile as I realised I couldn't even get the number of colours right for a 24 bit image (the single biggest error ;) )
  3.  
    This is all really cool information, what I understand of it anyway :-). Problem is, it doesn't address.t he issue I was having at the time.

    If the problem had been just the size of my image (and admittedly, it was too big) I would have received the 'empty image that I got later.

    It in the 5 months I've been here, I've never had a post attempt result in opening the format for starting a new.discussion.

    But that is what was happening. I tried to post on an already existing thread, and instead ended up with the windows w open to start a new discussion.

    How.could that.have happened?
    •  
      CommentAuthorDogtag
    • CommentTimeAug 2nd 2016
     
    Gremlins.

    *drops mic*
    • CommentAuthorLoopysue
    • CommentTimeAug 2nd 2016 edited
     
    Damn! how did they get out! Must remember to check my head for holes ;)

    @ Storm: I was having problems trying to upload one of the MC maps the other day. It just wouldn't load, and I was suddenly logged out of the site altogether! Half an hour later everything was fine. So maybe there was some kind of server glitch somewhere pretty major and it affected both of us on opposite sides of the Atlantic?
    •  
      CommentAuthorMonsen
    • CommentTimeAug 2nd 2016
     
    This error does usually occur because of file size. The forum is unfortunately not very well behaved when it comes to error messages for this particular issue. How large was the image you were trying to post? The actual limit for the forum is actually set a bit higher than the 1024 kb mentioned by Ralf (This is the limit we ask you to stick to though), but if the image is too large, it will hit the hard limit.
  4.  
    I don't remember, I ended up settings. It up as a JPEG, so it's.cool.