WIA and Webcams

Glenn Keeler

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May 8, 2013, 12:09:43 AM5/8/13

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I have been exploring replacing TWAIN access to Logitech webcams with WIA. Since Logitech no longer supports TWAIN, particularly under Win7, this appears to be my only option!

I have been trying a WIAAcquireImage function from the post below.

https://groups.google.com/d/msg/comp.lang.clipper.visual-objects/-KTl8UaYffE/KOKqnuKKl1YJ

However, under VO 2.8 SP3 the constants in this function are not recognized. So I am clearly missing something.

Does anyone have experience with WIA under VO who can provide some pointers?

Gustavo Biasone

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May 8, 2013, 11:23:20 AM5/8/13

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Hi Glenn,

These are the constants (strings) for FormatID:

wiaFormatBMP ({B96B3CAB-0728-11D3-9D7B-0000F81EF32E})
FormatID for the Microsoft® Windows® Bitmap (BMP) format.

wiaFormatPNG ({B96B3CAF-0728-11D3-9D7B-0000F81EF32E})
FormatID for the Portable Network Graphics (PNG) format.

wiaFormatGIF ({B96B3CB0-0728-11D3-9D7B-0000F81EF32E})
FormatID for the Graphics Interchange Format (GIF) format.

wiaFormatJPEG ({B96B3CAE-0728-11D3-9D7B-0000F81EF32E})
FormatID for the JPEG format.

wiaFormatTIFF ({B96B3CB1-0728-11D3-9D7B-0000F81EF32E})
FormatID for the Tagged Image File Format (TIFF) format.

HTH,
Gustavo Biasone

Glenn Keeler

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May 8, 2013, 2:06:43 PM5/8/13

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On Wednesday, May 8, 2013 9:23:20 AM UTC-6, Gustavo Biasone wrote:

> These are the constants (strings) for FormatID:

Thanks Gustavo. These are helpful. I think I have the other constants I need:

WIA_INTENT_IMAGE_TYPE_COLOR 0x00000001
Preset properties for color content.

WIA_INTENT_IMAGE_TYPE_GRAYSCALE 0x00000002
Preset properties for grayscale content.

WIA_INTENT_IMAGE_TYPE_TEXT 0x00000004
Preset properties for text content.

WIA_INTENT_MINIMIZE_SIZE 0x00010000
Preset properties to minimize image size.

WIA_INTENT_MAXIMIZE_QUALITY 0x00020000
Preset properties to maximize image quality.

WIA_INTENT_BEST_PREVIEW 0x00040000
Specifies the best quality preview.

Glenn Keeler

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May 13, 2013, 10:42:30 PM5/13/13

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On Wednesday, May 8, 2013 12:06:43 PM UTC-6, Glenn Keeler wrote:
> On Wednesday, May 8, 2013 9:23:20 AM UTC-6, Gustavo Biasone wrote:
>
> Thanks Gustavo. These are helpful. I think I have the other constants I need:

WIA was an exciting little diversion, but as it turns out it doesn't do the one thing I am after, which is capturing an image from a webcam. My clients are all shifting to Windows 7, which apparently limits WIA to scanners.

DirectShow appears to offer what I need, but I am having trouble finding an example syntactically close enough to VO to get me going. Have any of you worked with DirectShow in VO?

Gustavo Biasone

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May 14, 2013, 10:54:41 AM5/14/13

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Hi Glenn,

I did a webcam capture sample program long time ago. Not sure if it works on W7 and above but you can give it a try:

http://www.voers.com.ar/down/Capturavideo.zip

It uses Windows AVICap video capture.

PD: Most code comments are in Spanish.

HTH
Gustavo Biasone

Glenn Keeler

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May 19, 2013, 11:03:24 PM5/19/13

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On Tuesday, May 14, 2013 8:54:41 AM UTC-6, Gustavo Biasone wrote:
> Hi Glenn,
>
> I did a webcam capture sample program long time ago. Not sure if it works on W7 and above but you can give it a try:
>
> http://www.voers.com.ar/down/Capturavideo.zip
>
> It uses Windows AVICap video capture.
>
> PD: Most code comments are in Spanish.

Gustavo,

Do you have any idea why this will work the first run, but not subsequently?

Gustavo Biasone

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May 20, 2013, 12:54:03 PM5/20/13

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Hi Glenn,

Try reinstalling webcam drivers.
I tested it today with an old Philips USB webcam on W7 32 bits. I start/stop video preview multiple times and it works without problem here.