[AccessD] Resize pictures

We store pictures by the 10s of thousands annually for construction as well.  I'm usually leery of down sampling captured files.  In my opinion, there in no point in going higher than about a 5 megapixel sensor with a 1/2.5" sensor typical of most compact cameras.  These typically give us 1.5 to 2 megapixel JPG images.  The problem is that consumers are stupidly driving demand for higher megapixel cameras and it's becoming impossible to get a compact camera that provides a useful sized image.  The system resolution is the reciprocal of the sum of the reciprocals of the factors leading to resolution.  The small sensors result in small physical apertures that result in diffraction issues and if you take into account the physical size of dust in relation to sensor size, both on optics and on the sensor, you get a dog's breakfast.

 

Taking the sensor resolution, the lens resolution and the monitor resolution and summing their reciprocals and factoring in some interpolation for the conversions, it turns out that a lens that is capable of 100 lines/mm of resolution will yeild a system resolution of no better than 90 lines/mm whether you have 5 megapixels or a million megapixels.  No matter if you have a billion megapixels, the image can never quite reach 100 limes/mm, and less at smaller diffraction limited apertures.  Another factor with the small sensors is the amount of digital noise in low light situations.  Given a pixel that has 8 times the area on a larger sensor, the chances of 1 random photon toggling a level matches 8 random photos on the larger sensor.  The amount of image generated by noise is a fraction of the noise as the sensor size increases.

 

Downsizing an image by an integer ratio cuts out on interpolation fuzziness whereas downsizing by a factor 1.5 or 2.3 is going to make more of a mess of the apparent resolution of the resized image.  An exagerated example of this is what happens when you take an LCD set for 1024*768 and change it to 640*480.  Far better to take 1200*1600 to 600*800 with an even number ratio.

 

Given that construction documentation is such an important element of the business these days, we have outsourced much of the documentation to a company known a Multivista.  They take pictures on a specified schedule from points in specified directions all mapped on a construction blue print.  Your interface is to click on a point on the blue print, choose a direction and day and you can see where the wiring was laid, on which day, on which floor...  We've used the services where circumstances warrant, for example, on a number of exterior masonry rehab projects.  We've adopted some of the concepts you can see at multivista.com for our own documentation philosophy.  They use Nikon DSLRs exclusively and high megapixels matter with DSLRs.  

 

I've standardized on Canon A590IS compact cameras on the last round of purchases as an inexpensive camera to issue to sites.  Although it is an 8 megapixel camera and not as rugged as water proof, dust proof and droppable cameras, they still don't survive and cost twice as much.  I've issued instructions to ensure the camera date/time is correct, audio record the photographer name on the SD card every time a photographer takes the camera and set a medium resolution right at the camera options menu level.  I find the camera resolution interpolation to JPG is generally superior to post camera processing.  You need the name of the photographer so he can swear the image is a fair representation of the scene he observed should you ever want to rely on the photo as evidence.  Although a 5 megapixel sensor would be superior in terms of image quality and noise to the 8 megapixels of the Canon, we wanted a camera that would take double A batteries, standard SD cards, have basic video capability, audio notes, a reasonable optical zoom (4X) and optical image stabilization.  Eight megapixels was the lowest count that we could get in a reasonably well built compact reasonably featured camera and I'd be happer to pay a bit more if only we could get it with 5 megapixels.  I think that pretty soon we will be able to get phone cameras to the point that they will meet our documentation needs.


Ciao Jürgen Welz

Edmonton, Alberta

jwelz at hotmail.com


 
> Date: Wed, 6 Oct 2010 00:28:27 -0400
> From: joeo at appoli.com
> To: accessd at databaseadvisors.com
> Subject: [AccessD] Resize pictures
> 
> I am developing an A2003 application for a division of a construction
> company that installs guardrails on highways. They have long term
> contracts with the Department of Transportation to fix/repair/replace
> guardrails that have been damaged. Part of the documentation that is
> required is to provide a "before" and an "after" picture for all
> repairs.
> 
> The application lets the user browse the memory card for the pictures
> and then copies them to the computer's disk. The original size of the
> pictures is 5-6mb. Not only will a lot of disk space be required to
> store the pictures, but pictures of this size take a lot of time to be
> scaled for forms and reports. Due to the number of pictures processed
> each day, it is not feasible for the user to manually resize the
> pictures before uploading. What I would like to do is to resize the
> pictures during this transfer process to about 10% of their original
> size.
> 
> Any suggestions or code snippets to resize the pictures are greatly
> appreciated.
> 
> Joe O'Connell