Bitmaps and Highlight Selection


Should bitmaps be treated as a special condition when Highlight Selection (Choose PowerCADD menu > Preferences > View > Highlight Selection) is enabled?


PowerCADD v6 and Mac OS? X Panther
PowerCADD v7 and Mac OS X Tiger (10.4.4) or newer recommended


A special condition doesn't seem necessary since the there are only a few conditions where a bitmap alone would want to be selected and the behavior now seems predictable when Highlight Selection is Enabled. Note that while the specific points below mention bitmaps, the same condition is true for PICT? or PDF? objects -- they all react in the same, consistent, fashion as noted here.

In looking at whether a special case exists for treating bitmaps uniquely when Highlight Selection is Enabled, it seems to a good start point is to evaluate how bitmaps are treated now in various common drawing conditions. A few of those conditions are discussed below.

multiple selections: A related article on this site describes that multiple selections (a bitmap plus an object/s above it) behave correctly in that objects on layers above the bitmap will render to screen when selected. There is a nuance where objects on the same layer as the bitmap become obscured -- however for drawing management reasons large bitmaps are typically always on their own layer so this seems to be a non-issue in that context.

move by drag: These articles (here and here ) describe how to make the selected bitmap/s transparent in that condition without turning off Highlight Selection.

resize: bitmaps becomes transparent during a drag to resize operation. This presumes PowerCADD menu > Preferences > View > Transparent Drawing is enabled which seems like a reasonable presumption since we can't have a discussion of Transparency? of bitmaps or any object if those preferences are disabled.

crop: bitmaps becomes transparent during a crop operation

deleting: clearly not an issue for transparency -- select the item and delete it.

apply bitmap effect: (choose Tool menu > Apply Bitmap Effect...) Transparency when selected doesn't seem important in this condition since only the bitmap is selected for the effect and the preview is specific to the QuickTime window, not the entire drawing window. After applying the QT Effect the item is rendered to screen normally when deselected

applying bitmap transition tools: (Bitmap Effect Tool and Bitmap Transformation Tool) Transparency of the selected bitmap might be important if the 4 sided polygon it's being mapped to is above it. However it seems more likely the polygon being mapped to is either adjacent it or can be easily moved for this single condition

Print Selection: This is a bit of an odd one. Selecting only a bitmap to define the region to be printed (for example for Selected Object/Fit to Page) will obscure other data above it which will in fact be printed. One could argue it's not consistent with a WYSIWYG? printing environment but this seems like a case where having a unique print region layer (with a rectangle or 2 snap points) fixes the condition and has other management benefits.

Consistency: This might be an issue as being a case for a special condition. A filled object (e.g. rectangle solid red) does not obscure data when selected and Highlight Selection is enabled. Then again, the rectangle can be edited (e.g. to change fill pattern or color) so one needs to see it in context. Since bitmaps become transparent when edited as described in other points above perhaps things are consistent in that context and the need for a special condition isn't necessary after all.

Other conditions may apply that aren't described above but it seems those are the majority of conditions which seem to work even if Highlight Selection is enabled.

The other part of the question

For the sake of discussion, let's presume a case can be made to treat bitmaps as a special condition. How should the bitmap be treated if not as described above?

Some immediate thoughts are:

Make the bitmap transparent: This already seems to be happening now but the bitmap could automatically be rendered as transparent when selected and Highlight Selection preference is enabled. The down side to this might be a significant performance hit since that transparent preview needs to be 'built' before it can be rendered to screen. In light of the fact many users now are running Mac OS X and PowerCADD 6 on legacy machines, this may not be a practical solution. In PowerCADD 7 running in OS X on newer hardware might not be adversly affected.

Show only a bounding box: When a bitmap is selected, a bounding box could be shown instead of the content of the bitmap. This solution has the potential of being very fast with respect to performance and could benefit users on new and legacy hardware. Further, it seems this could be an application level preference which is not directly related to Highlight Selection. That is, the preference would be a View preference which could allows users to always render selected bitmaps as 'bounding boxes only' (verses showing transparent content). This might have more merit that attempting to link things with the current Highlight Selection Preference. Clearly, if this feature were enabled, then one needs to go back and consider the implications of what happens when bitmaps are cropped or resized --a condition where a full verses bounding box only preview is essential to performing the task.

Low Rez Preview: Rather than a simple empty bounding box (which is potentially scary for a user to see) a low resolution preview might be the other model to consider. When a bitmap is selected, rather the rendering a high quality preview (currently the case), a low resolution - pixelated - preview may be faster to render. Of course this is also a potentially scary notion for many users since they click on an item and it changes on screen and they may think it's potentially destructive. Still, it might be worth considering - look at Apple's iPhoto for example which generates pixelated previews which become sharper after scrolling or loading has completed.

Similar to Hide Dimensions/Hatches/Text: (PowerCADD menu > Preferences > View // or // View menu > Hide Text / Hide Hatch / Hide Dimensions). The existing feature to hide Text, Dimensions and Hatching is currently in place to help tweak performance. Given this precedent, is the concept of a "Hide Bitmap" which would still render the bounding box (or some other mode of visual feedback) when selected any different? It seems they are all related at a conceptual level as they hide information from the user which is intended to help improve performance.


Based on the current behavior of bitmaps when Highlight Selection is enabled, there does not appear to be a case for treating them as special under those conditions. However, for general performance reasons, having a user preference which allows bitmaps to be displayed as transparent (currently the case) or as bounding box only or low resolution preview may be a direction worth pursing which would benefit system and application performance in general for every user rather than only those users who work with Highlight Selection enabled. Give we already have the ability to Hide Hatch/Text/Dimensions perhaps a logical precedent has been set and users would be comfortable (not surprised or shocked) with the idea of a 'hidden bitmap' which somehow shows only an outline.

Ultimately it comes down to clarity of communication with the user. The current model is very communicative and clear -- essentially not broken or lack of a better description. Still, there's always room for improvement and discussion is the only way to test ideas.

We hope that helps

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