Background
As camera resolutions get higher and higher VB6's native image manipulation can get bogged down. This is especially true if you need to do some processing on he thumbnails such as dealing with odd sizes, portrait images, and so on. If you want to create a "viewer" based on one of the ListView controls and ImageList controls (v. 6 or v. 5) then you need to deal with mask-transparency and you might want an outline border.
While dropping down to API calls is fastest, the code can get complex making it harder to tailor even a known-working sample. One alternative is to make use of the WIA 2.0 Library available for XP SP1 and later and already installed as part of Vista or later.
With WIA you also have easy access to JPEG image files' embedded thumbnail image. These are created by many cameras now and can sometimes be optionally inserted using image editing software. When available, these prescaled thumbnails can be used as-is or as the basis for scaling to a specific desired thumbnail size. Even if you rescale it this may save time over scaling the entire full-size image.
Requirements
Since I'm using WIA 2.0 your computer must be running Windows XP SP1 or later. For XP you may have to download and install WIA 2.0 first. However:
Purpose
The Windows Image Acquisition (WIA) Automation Layer is a full-featured image manipulation component that provides end-to-end image processing capabilities. The WIA Automation Layer makes it easy to acquire images from digital cameras, scanners, or Web cameras, and to rotate, scale, and annotate your image files. The WIA Automation Layer supersedes the WIA Scripting Model provided by Windows Image Acquisition (WIA) 1.0.
Developer audience
The WIA Automation Layer API is designed for use by Microsoft Visual Basic 6.0, Active Server Pages (ASP), and scripting programmers.
Run-time requirements
Applications that use the WIA Automation Layer API require Windows Vista or later. Earlier versions of Windows are not supported.
What does this mean?
It means now that Windows 8 is out, Windows XP is on "death watch" and Microsoft has begun removing download links for many XP add-ons.
You'll probably have to scrounge the "Windows® Image Acquisition Automation Library" download from some 3rd party if you failed to get it while it was hot (i.e. in the last 6 years or so).
The WIA 2.0 Automation Library documentation is found in the Windows SDK for Vista (or later) documentation (help) files.
Of course those developing on Vista (the last release officially supporting VB6 development anyway, and in my opinion the best) have no problem except for deployment.
But even then if you want to deploy your programs downlevel to XP SP1 through SP3 you'll want the WIAAutSDK.zip download. It contains a CHM document - but more importantly a redistributable wiaaut.dll that works on XP systems!
MakeThumbs.cls
This is a class wrapping several WIA objects that can be used to accept a photo/image file name and create a thumbnail StdPicture from it ready for adding to an ImageList control.
The class has several properties you set:
Then you call the InitThumbs method to create the backdrop image containing the outline and the mask.
From there you can repeatedly call the FetchThumb method passing an image file name, getting back a StdPicture of the finished thumbnail image.
Use the result with any image control that has a Picture property or method argument and supports a mask color for transparency. The more obvious choices are probably ImageList controls used with a ListView or TreeView control.
JpegThumbs.vbp
This is a sample VB6 project using MakeThumbs. You browse to a folder containing images and then it loads and displays thumbnail images for all of the image file types it supports into an ImageList and ListView. Pretty simple, and the only gingerbread here is the ability to select among 3 thumbnail sizes.
Speed
I won't lie and call this a speed demon, though most of the time will probably be disk I/O. Requesting the same folder (or changing the thumbnail size after loading it once) may be twice or 3 times as quick due to disk caching.
A "first load" here seems to take about 1/8th of a second per image file for 3 to 4MB JPEGs. Doing the same steps using only VB6 native image processing techniques took me substantially longer, closer to 4 seconds per image. However I may have been using some poor techniques there too.
InitThumbs is slow by nature and I wish I had a better way to build the backdrop. But you only need to call it once when changing the dimension or color properties, not for every loaded image.
The Attachment
This contains the JpegThumbs project, including the MakeThumbs class module.
As camera resolutions get higher and higher VB6's native image manipulation can get bogged down. This is especially true if you need to do some processing on he thumbnails such as dealing with odd sizes, portrait images, and so on. If you want to create a "viewer" based on one of the ListView controls and ImageList controls (v. 6 or v. 5) then you need to deal with mask-transparency and you might want an outline border.
While dropping down to API calls is fastest, the code can get complex making it harder to tailor even a known-working sample. One alternative is to make use of the WIA 2.0 Library available for XP SP1 and later and already installed as part of Vista or later.
With WIA you also have easy access to JPEG image files' embedded thumbnail image. These are created by many cameras now and can sometimes be optionally inserted using image editing software. When available, these prescaled thumbnails can be used as-is or as the basis for scaling to a specific desired thumbnail size. Even if you rescale it this may save time over scaling the entire full-size image.
Requirements
Since I'm using WIA 2.0 your computer must be running Windows XP SP1 or later. For XP you may have to download and install WIA 2.0 first. However:
Quote:
Purpose
The Windows Image Acquisition (WIA) Automation Layer is a full-featured image manipulation component that provides end-to-end image processing capabilities. The WIA Automation Layer makes it easy to acquire images from digital cameras, scanners, or Web cameras, and to rotate, scale, and annotate your image files. The WIA Automation Layer supersedes the WIA Scripting Model provided by Windows Image Acquisition (WIA) 1.0.
Developer audience
The WIA Automation Layer API is designed for use by Microsoft Visual Basic 6.0, Active Server Pages (ASP), and scripting programmers.
Run-time requirements
Applications that use the WIA Automation Layer API require Windows Vista or later. Earlier versions of Windows are not supported.
It means now that Windows 8 is out, Windows XP is on "death watch" and Microsoft has begun removing download links for many XP add-ons.
You'll probably have to scrounge the "Windows® Image Acquisition Automation Library" download from some 3rd party if you failed to get it while it was hot (i.e. in the last 6 years or so).
The WIA 2.0 Automation Library documentation is found in the Windows SDK for Vista (or later) documentation (help) files.
Of course those developing on Vista (the last release officially supporting VB6 development anyway, and in my opinion the best) have no problem except for deployment.
But even then if you want to deploy your programs downlevel to XP SP1 through SP3 you'll want the WIAAutSDK.zip download. It contains a CHM document - but more importantly a redistributable wiaaut.dll that works on XP systems!
MakeThumbs.cls
This is a class wrapping several WIA objects that can be used to accept a photo/image file name and create a thumbnail StdPicture from it ready for adding to an ImageList control.
The class has several properties you set:
Set ThumbWidth & ThumbHeight to dimensions (in pixels) for the thumbnails. These dimensions include the 2px-wide border.
Set FrameColor to the desired frame color for the rectangular outline. This outline will be 1px wide with a 1px inner border of the MaskColor.
Set MaskColor to the transparency mask color to use for padding around the scaled thumbnail image from the source JPEG image.
Set FrameColor to the desired frame color for the rectangular outline. This outline will be 1px wide with a 1px inner border of the MaskColor.
Set MaskColor to the transparency mask color to use for padding around the scaled thumbnail image from the source JPEG image.
Then you call the InitThumbs method to create the backdrop image containing the outline and the mask.
From there you can repeatedly call the FetchThumb method passing an image file name, getting back a StdPicture of the finished thumbnail image.
Use the result with any image control that has a Picture property or method argument and supports a mask color for transparency. The more obvious choices are probably ImageList controls used with a ListView or TreeView control.
JpegThumbs.vbp
This is a sample VB6 project using MakeThumbs. You browse to a folder containing images and then it loads and displays thumbnail images for all of the image file types it supports into an ImageList and ListView. Pretty simple, and the only gingerbread here is the ability to select among 3 thumbnail sizes.
Speed
I won't lie and call this a speed demon, though most of the time will probably be disk I/O. Requesting the same folder (or changing the thumbnail size after loading it once) may be twice or 3 times as quick due to disk caching.
A "first load" here seems to take about 1/8th of a second per image file for 3 to 4MB JPEGs. Doing the same steps using only VB6 native image processing techniques took me substantially longer, closer to 4 seconds per image. However I may have been using some poor techniques there too.
InitThumbs is slow by nature and I wish I had a better way to build the backdrop. But you only need to call it once when changing the dimension or color properties, not for every loaded image.
The Attachment
This contains the JpegThumbs project, including the MakeThumbs class module.