Variations in JPG compression?

Last week a friend sent a photo from an iPhone.
It was horrendous quality. But instead of seeing
visible rectangular grids typical of JPG over-compression,
what I saw looked like extreme dithering -- like a
gradient displayed at 256 colors. I wondered whether
perhaps Apple had come up with a new way to reduce
JPGs so that they look better on tiny screens. It seemed
to make sense. The dithering probably won't look as bad
as rectangle grids at very small size reduction.

That made me wonder why Apple's photo sending
app doesn't offer an option for "send to phone" or
"send to non-phone". (Essentially, send for thumbnail
view or send for full image view.)

Anyone know more about this? Am I seeing a new
method of JPG compression? Here's a photo I saw
last night that shows both effects:

http://media.npr.org/assets/img/2015...-s1100-c15.jpg

In the lower right, especially, can be seen large areas
dithered into single-color blocks, while the more typical
hatchmark rectangles can be seen around the VW insignia.

In article , Mayayana
wrote:

Last week a friend sent a photo from an iPhone.
It was horrendous quality. But instead of seeing
visible rectangular grids typical of JPG over-compression,
what I saw looked like extreme dithering -- like a
gradient displayed at 256 colors. I wondered whether
perhaps Apple had come up with a new way to reduce
JPGs so that they look better on tiny screens. It seemed
to make sense. The dithering probably won't look as bad
as rectangle grids at very small size reduction.

no.

That made me wonder why Apple's photo sending
app doesn't offer an option for "send to phone" or
"send to non-phone". (Essentially, send for thumbnail
view or send for full image view.)

they offer a choice of sizes with a reduced size being the default so
that people don't get giant images in their email but the full size can
be sent if desired.

| That made me wonder why Apple's photo sending
| app doesn't offer an option for "send to phone" or
| "send to non-phone". (Essentially, send for thumbnail
| view or send for full image view.)
|
| they offer a choice of sizes with a reduced size being the default so
| that people don't get giant images in their email but the full size can
| be sent if desired.

I noticed they seem to offer 3 sizes -- small,
medium and large -- with KB listed. But I'm
not talking about final size. I'm wondering if
they're using different compression methods
for phone and, if so, whether there's an option.

Partly I'm just curious about the dithering, but
I also wonder whether I can tell iPhoners to
choose between compression methods in order
to send me a better picture.

Are you saying there's no new method of
compression? If not then I wonder what accounts
for the apparent dithering. If I use *very* extreme
compression on an image I still don't see dithered
rectangles.

In article , Mayayana
wrote:

| That made me wonder why Apple's photo sending
| app doesn't offer an option for "send to phone" or
| "send to non-phone". (Essentially, send for thumbnail
| view or send for full image view.)
|
| they offer a choice of sizes with a reduced size being the default so
| that people don't get giant images in their email but the full size can
| be sent if desired.

I noticed they seem to offer 3 sizes -- small,
medium and large -- with KB listed. But I'm
not talking about final size. I'm wondering if
they're using different compression methods
for phone and, if so, whether there's an option.

they aren't and there isn't.

Partly I'm just curious about the dithering, but
I also wonder whether I can tell iPhoners to
choose between compression methods in order
to send me a better picture.

no.

Are you saying there's no new method of
compression?

yes. it's a standard high quality jpeg, just like any other camera.

If not then I wonder what accounts
for the apparent dithering. If I use *very* extreme
compression on an image I still don't see dithered
rectangles.

bull**** you don't.

if you set the quality level even moderately low, the jpeg looks like
crap.

here's an easy way to compa
http://regex.info/blog/lightroom-goodies/jpeg-quality

On 2015-09-25 18:29:55 +0000, "Mayayana" said:

| That made me wonder why Apple's photo sending
| app doesn't offer an option for "send to phone" or
| "send to non-phone". (Essentially, send for thumbnail
| view or send for full image view.)
|
| they offer a choice of sizes with a reduced size being the default so
| that people don't get giant images in their email but the full size can
| be sent if desired.

I noticed they seem to offer 3 sizes -- small,
medium and large -- with KB listed. But I'm
not talking about final size. I'm wondering if
they're using different compression methods
for phone and, if so, whether there's an option.

I don't know about your friend's iPhone, but my iPhone 5S running iOS
9.01 shows 4 sizes (Small, Medium, Large, and Actual size) and no
indication of compression method.
https://db.tt/lAorCDzu

Partly I'm just curious about the dithering, but
I also wonder whether I can tell iPhoners to
choose between compression methods in order
to send me a better picture.

Are you saying there's no new method of
compression? If not then I wonder what accounts
for the apparent dithering. If I use *very* extreme
compression on an image I still don't see dithered
rectangles.


--
Regards,

Savageduck

In article ,
"Mayayana" wrote:

Last week a friend sent a photo from an iPhone.
It was horrendous quality. But instead of seeing
visible rectangular grids typical of JPG over-compression,
what I saw looked like extreme dithering -- like a
gradient displayed at 256 colors. I wondered whether
perhaps Apple had come up with a new way to reduce
JPGs so that they look better on tiny screens. It seemed
to make sense. The dithering probably won't look as bad
as rectangle grids at very small size reduction.

That made me wonder why Apple's photo sending
app doesn't offer an option for "send to phone" or
"send to non-phone". (Essentially, send for thumbnail
view or send for full image view.)

Anyone know more about this? Am I seeing a new
method of JPG compression? Here's a photo I saw
last night that shows both effects:

http://media.npr.org/assets/img/2015...84bade8a6ac60c
960cb2e5a76d0-s1100-c15.jpg

In the lower right, especially, can be seen large areas
dithered into single-color blocks, while the more typical
hatchmark rectangles can be seen around the VW insignia.

JPEG is lossy so there are many different algorithms for reducing the
data size.

https://en.wikipedia.org/wiki/JPEG

A JPEG is chopped up into 8x8 blocks and then a set of frequency
patterns is extracted from each block. The weights of those frequency
patterns is then altered with the goal of creating simpler (easily
compressed numbers) without hurting the image too much. In the image
you've provided, the compressor simply set most everything to zero.
That makes big colored blocks and ripples.

--
I will not see posts from astraweb, theremailer, dizum, or google
because they host Usenet flooders.

| JPEG is lossy so there are many different algorithms for reducing the
| data size.
|
| https://en.wikipedia.org/wiki/JPEG

Thanks. I didn't realize there was so much possible
variation in compression techniques. (Though I
can't say I really understand the details.)

I found this at your link:

"Some programs allow the user to vary the amount by which individual blocks
are compressed. Stronger compression is applied to areas of the image that
show fewer artifacts. This way it is possible to manually reduce JPEG file
size with less loss of quality."

So perhaps Apple has come up with their
own particular variation for optimizing their
small-size images. It seems odd, though,
that they don't then provide options for the
target audience -- phone vs large screen.

One factor there is that -- independent
of compression method/degree -- they've
made the decision to render, say, an 1100 px wide
image at full size, with gross artifacts, rather than
shrinking the original to maybe a 400-600 px
wide image with fair quality, in order to reach a
target file size. That makes sense if the viewing
display will be 300+ ppi and the image will then
be deleted, but it works very poorly when the
viewing display is a computer monitor, or the
recipient may actually want to save the photo.

Then again, I suppose the iPhone user often wouldn't
be able to make such decisions as to the best
optimization. Even if they know how the image will
be viewed, the fact that they're letting iPhone edit
the photo implies that either they don't care or are
not capable to do it themselves. And where photos
are merely viewed as thumbnails between phones
and then deleted, I guess image quality really isn't
relevant.

In article , Mayayana
wrote:

| JPEG is lossy so there are many different algorithms for reducing the
| data size.
|
| https://en.wikipedia.org/wiki/JPEG

Thanks. I didn't realize there was so much possible
variation in compression techniques. (Though I
can't say I really understand the details.)

I found this at your link:

"Some programs allow the user to vary the amount by which individual blocks
are compressed. Stronger compression is applied to areas of the image that
show fewer artifacts. This way it is possible to manually reduce JPEG file
size with less loss of quality."

So perhaps Apple has come up with their
own particular variation for optimizing their
small-size images. It seems odd, though,
that they don't then provide options for the
target audience -- phone vs large screen.

as you have been told, apple offers to send the photo in one of several
sizes. the full resolution is always available.

One factor there is that -- independent
of compression method/degree -- they've
made the decision to render, say, an 1100 px wide
image at full size, with gross artifacts, rather than
shrinking the original to maybe a 400-600 px
wide image with fair quality, in order to reach a
target file size. That makes sense if the viewing
display will be 300+ ppi and the image will then
be deleted, but it works very poorly when the
viewing display is a computer monitor, or the
recipient may actually want to save the photo.

the full resolution is always saved. it might be downsized for sending
if the user chooses that. the compression quality is always high.

Then again, I suppose the iPhone user often wouldn't
be able to make such decisions as to the best
optimization. Even if they know how the image will
be viewed, the fact that they're letting iPhone edit
the photo implies that either they don't care or are
not capable to do it themselves. And where photos
are merely viewed as thumbnails between phones
and then deleted, I guess image quality really isn't
relevant.

the user can and does make such decisions.

your feeble attempt to bash apple has failed.

by the way, it's pretty much the same thing on android.

On 9/27/2015 12:09 PM, nospam wrote:
In article , Mayayana
wrote:

| JPEG is lossy so there are many different algorithms for reducing the
| data size.
|
| https://en.wikipedia.org/wiki/JPEG

Thanks. I didn't realize there was so much possible
variation in compression techniques. (Though I
can't say I really understand the details.)

I found this at your link:

"Some programs allow the user to vary the amount by which individual blocks
are compressed. Stronger compression is applied to areas of the image that
show fewer artifacts. This way it is possible to manually reduce JPEG file
size with less loss of quality."

So perhaps Apple has come up with their
own particular variation for optimizing their
small-size images. It seems odd, though,
that they don't then provide options for the
target audience -- phone vs large screen.

as you have been told, apple offers to send the photo in one of several
sizes. the full resolution is always available.

One factor there is that -- independent
of compression method/degree -- they've
made the decision to render, say, an 1100 px wide
image at full size, with gross artifacts, rather than
shrinking the original to maybe a 400-600 px
wide image with fair quality, in order to reach a
target file size. That makes sense if the viewing
display will be 300+ ppi and the image will then
be deleted, but it works very poorly when the
viewing display is a computer monitor, or the
recipient may actually want to save the photo.

the full resolution is always saved. it might be downsized for sending
if the user chooses that. the compression quality is always high.

Then again, I suppose the iPhone user often wouldn't
be able to make such decisions as to the best
optimization. Even if they know how the image will
be viewed, the fact that they're letting iPhone edit
the photo implies that either they don't care or are
not capable to do it themselves. And where photos
are merely viewed as thumbnails between phones
and then deleted, I guess image quality really isn't
relevant.

the user can and does make such decisions.

your feeble attempt to bash apple has failed.

by the way, it's pretty much the same thing on android.


Please explain how his posting can be even remotely considered a bash of
Apple. I regularly will bash apples to make apple cider.



--
PeterN