More precise quality for saveimage.

[CONVERT]

Hello,

The saveimage command allows quality from 0 to 10 by step of 1.

Would it be possible to set quality from 0 to 100 in a future version of PB?

I build photos web sites. Sometimes 8 is not enough, and 9 gives sometimes big file. I would try 8.5, as it is possible in photo softs.

Thanks
Jean.

[nco2k]

0 to 100 ?!!??!

i really dont think, this is a good idea. i dont even know if this is possible due the jpeg format specifications.

if 8 is not enough for you, then use 9. with 9 i cant see any difference, if i dont zoom the image. so where is the problem. otherwise use 10. if 10 is not enough, you should be maybe using, a different format, like png, targa or tiff for example.

photoshop for example, provides a quality from 0-12.

p.s.: the size depends on the image itself. you can save two different files, one with a lot of stuff on it, the other with just few. save them both with the same flag and you will see, its a big difference in size, for each file. it depends on, how good the image can be compressed.

c ya,
nco2k

[PB]

> photoshop for example, provides a quality from 0-12

But Paint Shop Pro allows 1-100 for JPG quality, as do other apps and third
party tools (eg. the ever-popular NViewLib.dll). I think 1-100 is a standard.
I'd never seen just 1-10 except in PureBasic, so I can fully relate as to why
Convert's asking for it. Even one of my friends asked me why my app only
lets me select 1-10 for JPG saving; I told him they're 10%, 20%, and so on
up to 100%. He didn't like the explanation.

[nco2k]

@PB
yes maybe, but i think internal its really 0-100%. so maybe you should just check in your app the quality step.

something like:

Code: Select all

Quality.s = "74"
If Val(Quality) => 0 And Val(Quality) <= 100
  If Val(Mid(Quality, Len(Quality), Len(Quality))) => 5
    Debug Val(Mid(Quality, 1, Len(Quality) - 1)) + 1
  Else
    Debug Val(Mid(Quality, 1, Len(Quality) - 1))
  EndIf
EndIf

no but serious, i think the other apps do the same thing.

c ya,
nco2k

[Dare2]

I haven't tried this for a while but I recall that down the other end of the scale the differences are (were?) quite dramatic and can (could have?) use(d) some in-between value.

Besides, 1-100 sounds, um, intuitive.

[PB]

> Besides, 1-100 sounds, um, intuitive.

Isn't it meant to mean a percentage of the original quality? So if you saved
at 50%, then the saved image would only look half as good as the original.

[CONVERT]

Yes, 0 to 100.

It is the case of Ulead PhotoImpact, even in the old versions.

Code: Select all

An example with Ulead PhotoImpact 11,

for a 800 x 600 pixels JPEG (size in KB):

Quality       PB    Ulead
    8        111      140  (not quite good for mountains in the sky)
    8.5               158  (good quality)
    9        165      189  (good quality)

In fact, the 9 of PB is near of 8.5 of Ulead, in size and quality, and is sufficient.

So, you're right. It is not useful to have more precise quality.

Jean.

[Dare2]

I still like the idea of 1-100. Even if PureBasic fudges as per nco2k's example.

[PB]

Here's a procedure to convert a percentage (1-100) to PureBasic's range (1-10):

Code: Select all

Procedure SelectJPGSetting(percentage)
  purebasic.f=percentage/10
  If ValF(Mid(StrF(purebasic),2,9))>0.4 : roundup=1 : EndIf
  ProcedureReturn Round(purebasic,roundup)
EndProcedure

Debug SelectJPGSetting(74)
Debug SelectJPGSetting(75)

[blueznl]

and such a complex one at that!

[Blade]

This is what happens when a programmer have never seriously used a paint program

As correctly CONVERT stated:

I build photos web sites. Sometimes 8 is not enough, and 9 gives sometimes big file. I would try 8.5, as it is possible in photo softs.

The difference between 80% ( 8 ) and 90% ( 9 ) is huge: many times the quality difference can't be easily seen, but the file size is way bigger.
This is not linear too: between 50% or 60%, visually there is a big difference, but the file size doesn't change much. At higher quality level, the visual difference is low, and the file size difference is high.
So yes, we need a better control on file saving quality.

[nco2k]

@Blade
well i dont know, about any paint programms, because i am used to the professional photoshop and this is with no doubt the best app you can get.

if you want more control about the quality/size, you should better request for optimizations, like baseline and multipass.

i tried a 2.25mb wallpaper with different settings in photoshop:

Code: Select all

quality 8, baseline standard - 139kb
quality 8, baseline optimized - 136kb
quality 8, multipass 3 - 137kb
quality 8, multipass 4 - 137kb
quality 8, multipass 5 - 137kb

quality 9, baseline standard - 150kb
quality 9, baseline optimized - 145kb
quality 9, multipass 3 - 147kb
quality 9, multipass 4 - 147kb
quality 9, multipass 5 - 148kb

for me at least, there is no need for more precise quality control. i wont die if the file gets 10kb bigger.

but look at purebasic:

Code: Select all

purebasic quality 8 - 95.4kb
purebasic quality 9 - 125kb

and when i look at this:

Code: Select all

An example with Ulead PhotoImpact 11, 

for a 800 x 600 pixels JPEG (size in KB): 

Quality       PB    Ulead 
    8        111      140  (not quite good for mountains in the sky) 
    8.5               158  (good quality) 
    9        165      189  (good quality)

the size difference is pretty strange. so maybe ps has "only" 0-12 because the encoder is simple better and it would not take any big effect if they would have 0-100.

because the pb encoder is actually not the "best" one, maybe more precision control would be helpfull here.

but thats fred's decision anyway.

@CONVERT
can you email me the example file you tried, so i can test it with ps.

c ya,
nco2k

[CONVERT]

You can load the image from here:

http://pg.ctjean.com/tests/Out_ulead9157_100.JPG

It is a 800 x 600 photo. 449 KB.

Here is the code to test saveimage:

Code: Select all

; test quality saveimage

UseJPEGImageDecoder()
UseJPEGImageEncoder()

wfile_in$  = "Out_ulead9157_100.JPG"

If LoadImage(0,wfile_in$) = 0
  MessageRequester("Test save image quality","Err loadimage " + wfile_in$)
  End
EndIf

For quality = 80 To 90 Step 5
  wfile_dest$ = "OUT_" + Str(quality) + "_PB.JPG"
  w.f = quality / 10
  If SaveImage(0, wfile_dest$ , #PB_ImagePlugin_JPEG , w.f) = 0
    MessageRequester("Test save image quality","Err saveimage " + wfile_dest$ + " " + StrF(w.f,2))
  EndIf
Next quality

End

[CONVERT]

An add to my precedent message.

The true original photo is here:

http://pg.ctjean.com/tests/DSCN9157.JPG

2560 x 1920 (1,6 MB)

It shows many details (the houses in the village), and a difficult part to compress for jpeg (the sky just above the mountains).

It comes from a CoolPix 5700 in fine quality.

I used Ulead PhotoImpact 11 to resize it at 800 x 600, then saved in jpeg with 100 % quality, with no mask, mode progressive and subsampling = YUV411. These are the default options.

This gives http://pg.ctjean.com/tests/Out_ulead9157_100.JPG

800 x 600 (449 KB)

And I use this file to save it with PB, with 8 and 9 qualities.

[nco2k]

Code: Select all

photoshop quality 0, baseline standard - 47.9kb
photoshop quality 0, baseline optimized - 45.4kb

photoshop quality 1, baseline standard - 51.4kb
photoshop quality 1, baseline optimized - 49.1kb

photoshop quality 2, baseline standard - 61.9kb
photoshop quality 2, baseline optimized - 59.7kb

photoshop quality 3, baseline standard - 84.6kb
photoshop quality 3, baseline optimized - 81.0kb

photoshop quality 4, baseline standard - 97.5kb
photoshop quality 4, baseline optimized - 93.8kb

photoshop quality 5, baseline standard - 113.0kb
photoshop quality 5, baseline optimized - 109.0kb

photoshop quality 6, baseline standard - 137.0kb
photoshop quality 6, baseline optimized - 134.0kb

photoshop quality 7, baseline standard - 132.0kb <- strange, smaller than lvl6
photoshop quality 7, baseline optimized - 127.0kb <- strange, smaller than lvl6

photoshop quality 8, baseline standard - 169.0kb
photoshop quality 8, baseline optimized - 166.0kb

photoshop quality 9, baseline standard - 208.0kb
photoshop quality 9, baseline optimized - 206.0kb

photoshop quality 10, baseline standard - 267.0kb
photoshop quality 10, baseline optimized - 264.0kb

photoshop quality 11, baseline standard - 370.0kb
photoshop quality 11, baseline optimized - 365.0kb

photoshop quality 12, baseline standard - 524.0kb
photoshop quality 12, baseline optimized - 507.0kb


purebasic quality 0 - 8.28kb <- destroyes the image
purebasic quality 1 - 18.7kb
purebasic quality 2 - 31.7kb
purebasic quality 3 - 42.8kb
purebasic quality 4 - 52.3kb
purebasic quality 5 - 61.3kb
purebasic quality 6 - 71.3kb
purebasic quality 7 - 86.5kb
purebasic quality 8 - 110.0kb
purebasic quality 9 - 164.0kb
purebasic quality 10 - 452.0kb <- huge difference

i havent tested multipass, because i am too lazy.

in overall the pb size is smaller, but the quality is not that good. lvl8 is ok and lvl9 is good, but everything below is bad imho. the lvl9 -> lvl10 size difference is way too big. so yes, we need a more precise quality control. for me, 0-12 would be more than enough, but fine, if you guys want 0-100 then lets vote for 0-100.

p.s.: the saved image was destroyed by using lvl0.

@CONVERT
thanks for sharing.

c ya,
nco2k