[sane-devel] terrible (systematically corrupted) jpg at 1200dpi

Carsten Jensen tomse at tomse.dk
Wed Jan 28 19:09:48 UTC 2015

the circles with the dot in the middle that you're refering to in one of
your initial email
are the result of the print, an algorithm to adjust the brightness of
colours, and make the print cheap.
you can see them if you use a magnifying glass.

you see them now because of the high resolution and you can zoom in.

I must agree with Allan, I don't see anything wrong with the images either.


On 28-01-2015 19:58, m. allan noah wrote:
> I just looked at the top couple inches of both images in your
> launchpad bug report, and I dont see anything wrong with the files.
> allan
> On Wed, Jan 28, 2015 at 1:53 PM, ken <gebser at mousecar.com> wrote:
>> I already opened up a bug report on this:
>> https://bugs.launchpad.net/hplip/+bug/1415121, if anyone's interested.
>> On 01/28/2015 01:44 PM, ken wrote:
>>> What I wrote already in the prior email makes it clear this is a 1200dpi
>>> scanner.
>>> "4 pixels per dot" would correspond to 3 colors + a B/W bit for each
>>> dot-- what would be required for color scanning at 1200dpi.  "Pixel" is
>>> a rather slippery term.  Perhaps the tech should have said "sensel". But
>>> this was tier-one tech support after all, not a developer I was talking
>>> with.  And she had to look up that much.
>>> On 01/28/2015 10:33 AM, m. allan noah wrote:
>>>> "4 pixels per dot" is a meaningless statement. A dot is a pixel. You
>>>> would have to ask the hplip guys if they can get 1200 dpi out of this
>>>> scanner.
>>>> allan
>>>> On Wed, Jan 28, 2015 at 9:39 AM, ken <gebser at mousecar.com> wrote:
>>>>> On 01/28/2015 07:23 AM, m. allan noah wrote:
>>>>>> at least in lineart mode, the scanner maximum is 300dpi. Try scanimage
>>>>>> --mode=color --help
>>>>>> allan
>>>>> According to specifications published by HP, this scanner's hardware and
>>>>> optical resolution is 1200x1200 dpi.  I just called HP tech support to
>>>>> confirm this and was told this is correct and that, further, there
>>>>> are "4
>>>>> pixels per dot", meaning that the scanner handles both color and B/W
>>>>> at that
>>>>> resolution.  So I don't know why scanimage would report that 300dpi
>>>>> is the
>>>>> maximum resolution.

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