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  1.    #1  
    Hello,

    I know that the fixed focus camera on the Pre is not good for reading barcodes, but I'm interested in creating an app to DISPLAY barcodes (starting with store loyalty cards). The problem is that I'm not sure how well various bar code readers in stores will read off the screen (and don't want to waste too much of mine or anyone else's time if it won't work). If anyone is interested in helping me test this, just reply back here and/or PM me your email address. In particular, if you work in retail at some place with a barcode reader, I'd love to hear from you. Thanks.

    -Keith
  2. xtn
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    #2  
    I don't have any basis for what I'm about to say; it's just a guess...

    I strongly doubt that your standard bar code reader will read anything shown from a glossy LED screen. The little red laser is just going to get full reflection and read the screen as being completely white, regardless of what is displayed on it.

    Just my guess,
    xtn
  3.    #3  
    That's exactly my worry. I understand that sometimes the handheld barcode readers can read them better, though (some stores have them to scan stuff in carts, etc).

    -Keith
  4. #4  
    friend does it on his iPhone....works perfect. Just loaded pics of the cards on it.
  5.    #5  
    Yeah, I've heard about an app that does it on there too. It's something I've wanted to do for a while (pre-iPhone).

    If it works, is this something that other people would be interested in?

    -Keith
  6. #6  
    sounds good. i work in an autozone and although im on vacation this week i will try it next week with multiple items and the loyalty cards. i will let you know my results too.
  7.    #7  
    Quote Originally Posted by Runningwarrior08 View Post
    sounds good. i work in an autozone and although im on vacation this week i will try it next week with multiple items and the loyalty cards. i will let you know my results too.
    Excellent, thanks. I wanted to test out a couple sdks that will build barcodes so feel free to send/pm me the numbers from a barcode and I can send you an image to try to scan.

    -Keith
  8. #8  
    Okay. Will do. I will pm you with a few barcode numbers sometime next week.
  9. #9  
    Quote Originally Posted by Richardsonke View Post
    The problem is that I'm not sure how well various bar code readers in stores will read off the screen
    That entirely depends on which technology is used in the reader. A reader which uses a laser scan will NOT read any barcode off a screen. That is because a LCD screen is not a constant image. It just appears that way to our eyes because it refreshes faster than our eyes can see it go on and off. Not unlike a normal home A/C lightbulb which cycles on and off 60 times a second.

    The problem this causes for laser scanners is they don't read the whole image at one either -- they also scan the laser beam across the image using a rotating mirror to sweep the sensor across the path (its red line is not constant either). While the rate is too fast for our eyes to normally see, it does disrupt the ability to scan the barcode.

    On the other hand, some barcode scanners don't use a laser, but use imaging. They in essence take a picture of the barcode, then analyze it to decode the bars. Those CAN read barcodes off a screen, at least when the quality is good.

    So the answer to your question is it will all depend on what technology the scanner uses to read the barcode. The traditional red lasers CANNOT read them, due to the refresh rates of LCD screens.
  10. #10  
    I see what you are saying and it does make sense. But I can test this to be 100% sure because at the autozone I work we have laser scanner and the other type and I do not know what it is called but it uses the picture of the barcode, when trying to scan it shows a red blinking box instead of the line.
  11. #11  
    Quote Originally Posted by PreOwned View Post
    That entirely depends on which technology is used in the reader. A reader which uses a laser scan will NOT read any barcode off a screen. That is because a LCD screen is not a constant image. It just appears that way to our eyes because it refreshes faster than our eyes can see it go on and off. Not unlike a normal home A/C lightbulb which cycles on and off 60 times a second.
    Even expanding on that, I would believe that even if the LCD was more like the fixed "paper" displays, the majority of the bouch back would occur before the laser even reaches the LCD. So there would be no absorption of the the laser on black and it would look like a white piece of paper to the reader.
    Your Pre wants Word Whirl from the App Catalog.

    It told me.
  12.    #12  
    Quote Originally Posted by PreOwned View Post
    That entirely depends on which technology is used in the reader. A reader which uses a laser scan will NOT read any barcode off a screen. That is because a LCD screen is not a constant image. It just appears that way to our eyes because it refreshes faster than our eyes can see it go on and off. Not unlike a normal home A/C lightbulb which cycles on and off 60 times a second.
    Are you sure about that? That's true about CRT monitors (each pixel is only lit for a fraction of a second), but with a LCD, the pixels are lit the whole time, they are just refreshed (changed) every so many times a second. So, if the image isn't changing, the screen should not change. Please correct me if I'm wrong.

    I can see the reflective glass being an issue though.

    -Keith
  13. #13  
    Quote Originally Posted by Runningwarrior08 View Post
    I see what you are saying and it does make sense. But I can test this to be 100% sure because at the autozone I work we have laser scanner and the other type and I do not know what it is called but it uses the picture of the barcode, when trying to scan it shows a red blinking box instead of the line.
    The other two main types of scanners are CCD and cmos imaging. But I can assure you laser scanners will NOT read barcodes off a screen. I have dealt with barcode scanners for over a decade; it does not work.
  14. #14  
    I tried this with my membership card for the gym. I took a picture of the barcode with a good digital camera and put it on my phone, but the red laser line scanner at the gym could not read it at all.
  15. #15  
    I used an E-Ticket on my Pre to fly recently. Pull up the barcode on your Pre and put it up to the screen and it scans just like a piece of paper. I'm guessing airports don't use a standard barcode reader?
  16. #16  
    Quote Originally Posted by semprini View Post
    I used an E-Ticket on my Pre to fly recently. Pull up the barcode on your Pre and put it up to the screen and it scans just like a piece of paper. I'm guessing airports don't use a standard barcode reader?
    They use a "standard" barcode reader, they just don't use a laser based barcode reader. If the reader used imaging to read the code, it works just like you looking at the screen. The light being emitted from your backlight or reflected off the paper "powers" the scanner.

    A laser scanner shoots out a bright light (amplified by stimulated emission of radiation) and reads what bounces back. Take a bright light and shine it at your screen. Now look what bounces back. A bright light, with no screen data.
    Your Pre wants Word Whirl from the App Catalog.

    It told me.
  17. #17  
    Quote Originally Posted by Runningwarrior08 View Post
    I see what you are saying and it does make sense. But I can test this to be 100% sure because at the autozone I work we have laser scanner and the other type and I do not know what it is called but it uses the picture of the barcode, when trying to scan it shows a red blinking box instead of the line.
    That is an imaging scanner. I've uploaded PDFs of invoices onto my Pre and those scanners will read the barcodes just fine.
  18. #18  
    Just tested it, would not read any barcodes that i found online or the ones that i use to reprogram the scanner(which does infact read from my laptop with a matte finish LCD) the screen just reflects way too much light.

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