Media Data Formats Project

  Media Data Formats Project

For the first picture I starting dropping the colours with and without dithering. I actually seemed to really get away with going down to some low amount of colours
before the picture had become unacceptable to publish. The lowest I may have gone
would be 16 or even 15 but any further and it would be too far.

The first thing I did was re-sized the image so that it was 600x800 and the color palette was 256 colours. This didn't have any effect really. Also when I used the no dithering setting it didn't seem to make much of a difference

600x800 dithering

600x800 no dithering

The next step was to start dropping the amount of colours in the colour palette. The following are the results that I got when I lowered the palette from 256 to 128. Not really a big difference if any can be seen.

128 dithering

128 no dithering

 Next was changing the palette to 64 colours with and without dithering. even with such a drop in colours the image was still in very good condition.

64 dithering

64 no dithering

32 dithering

32 no dithering

This is where I really started to notice the quality of the images change noticeably. The effect of having a smaller colour palette along with the presence of dithering and the lack of it was much more profound. The main area that caught my attention to the difference in the appearance of the picture was the large yellow band at the top of the picture. The shading of it seemed to change quite a lot in comparison to the rest of the picture. Another effect that I observed was that the picture had gotten more fuzzy the smaller the palette got. I think if I was to publish a web page and had to include this picture I would most likely go with the 32 colour palette. I think it retains the quality whilst also not letting the file be too big.

16 dithering

16 no dithering

These next two pictures are here mainly to show that the difference in the quality of the images had gotten really sensitive to the minimizing of the colour palette. The quality of the picture takes a big hit even with the change in the palette only being lowered by one colour. I noticed parts of the picture where the colour would change and it was easy to see with a change of colour palette, sometimes the picture just seemed to be a bit distorted.

15 Dithering

15 no Dithering

14 no Dithering

14 Dithering

I have included a graph which corresponds to the change in colour palette vs the size of the file. Seeing as the initial size of the jpg was over 2mb and the highest size file for the gif was 348 kb I think the compression is a must have when you aren't relying heavily on the quality of the image.

	Size of File (kb)
Colours	Dithering	No Dithering
256	348	308
128	319	308
64	246	222
32	213	190
16	141	123
15	140	122
14	141	119

This is the 2nd picture. Again I think if I had chosen a picture that had a better variety of colours then the changes would be shown much better effect. The reason I have included the original jpg file with this set of pictures is because even with the conversion from jpg to gif I can see that the picture isn't as sharp as it was.This is especially noticeable with the tree at the front of the picture. The bushes are much sharper in the original than in the gif.

Original Jpg

256 no dithering

256 Dithering

As with the first picture I couldn't really notice much of a change if any at all when changing the colour palette to a lower size. Below I have the colour palette at 128 and I think this is almost the exact same as the 256 colour palette picture. There seems to be a trend of the pictures being able to cope well with being halved when the numbers are these large. Lets see what happens as I go lower with the amount of colours on the palette.

128 no Dithering

128 Dithering

64 Dithering

64 no Dithering

With the change from 128 colours to 64 colours I noticed that the picture almost had stayed completely the same except for one thing that stood out to me. This was that all the black areas in the picture now had converted to a kind of dark grey colour so this shows that colour had been deleted from the palette and it had a noticeable effect. The first that I have seen on this picture.

32 Dithering

32 no Dithering

Next thing to do was to change to 32 colours on the palette. The most immediate point of interest was that the picture now had lost some of the vibrancy it had before. It doesn't have the same sort of brightness that it had in the green area. This may be a problem as someone putting this picture may rely on the picture being as bright as possible.

16 no Dithering

16 Dithering

In comparison to the last picture this picture becomes unacceptable once the colour palette reached 16 colours. The colour all seems to mix together and this picture seems more like it has maybe a 6 colour palette rather than 16 and this surprised me bacuse the picture is dominated by green so I thought that it may get down to a much smaller colour palette than this.

If I were to publish this picture I would definitely avoid the 16 colour palette completely and maybe use the 64 colour palette. Better yet find a balance between the 32 and 64 colour palettes. This is what I did and I found that I got a good balance at 46 colours. I would go for the non dithered picture because the dithered version has some white dots in the black areas which aren't very nice to look at.

46 No Dithering

46 Dithering

I have included a graph which corresponds to the change in colour palette vs the size of the file. There really wasnt much of a difference in the sizes this time as you can see by the table and graph

	Size of File (kb)
Colours	Dithering	No Dithering
256	409	409
128	345	345
64	268	268
46	259	251
32	217	217
16	146	146

This is the 3rd picture that I chose. I think this was my best choice of image to show how the colour palette effects the image because it has a wider variety of colours than the other two pictures above.

This is the 3rd Picture. For this picture as all the others I had to resize it to 800x600 but it wasn't as straight forward as the others because it had to be cropped. Below is the original uncropped jpg version. As you can see I cropped the width of the image from left side.

Original

I was required to crop some from the sides in order to make the 800x600 requirement and this is what I was left with.

256 No Dithering

256 Dithering

128 No Dithering

128 Dithering

When I compared the first change in the size of the colour palette I could see a slight change straight away. It wasn't anything too drastic but it was noticeable none the less.  

64 No Dithering

64 Dithering

I found the picture started to really lose the sharpness that it had in the previous versions. It isn't taking the drop in colours quite as bad as I thought it would but still, all the subtle changes that I am noticing are really adding up and slightly taking away from the picture.

32 No Dithering

32 Dithering

This is where I found I would definitely stop lowering the size of the colour palette. I don't think I would even go with this size of colour palette as the picture becomes very cartoon like and the appeal of it as a whole just drops completely in my opinion. And seeing as the size of the file now is 109kb and the size of it with the 64 colours is 140 then I would just use the 64 colour palette because it isn't worth the drop in quality at all.

16 No Dithering

16 Dithering

I included these two images just to emphasise that the picture really is unclear and blurry at this low level, it can even be seen in the small pictures on the blog that's how bad it has gotten. I also have included a graph to illustrate the drop in size of the file with the minimizing of the colour palette.

I believe that in this assignment I have successfully outlined the that the change in palette size greatly affects the quality of the picture along with the size of the image also. You need to experiment to find the balance of size and quality. This kind of thing is quite important when we are publishing images on the web as it affects the loading of the page and the overall experience on the website so it is important to get the balance just right.