Image background transparency changes if computer has or hasn't Raster Design

[Anonymous]

Hi,

I've been having a issue with an image that has a transparent background.

The image is a 4 band GeoTIFF with 0.5x0.5 with no compression and I need the background to be transparent.

The image itself has a background transparency (NoData value if read in ArcGIS) and it shows correctly (see Figure 1) when I open the drawing in either with AutoCAD, AutoCAD LT or Civil 3D as long as the computer doesn´t have Raster Design installed).

Figure 1

However, in any computer with Raster Design installed the image shows the yellow background (see Figure 2)

Figure 2

I've been searching for a system variable or a Raster Design option but I can´t figure out a way to make the image to show as intended in every computer.

I've tried setting the background transparency with Raster Design and using different formats (ECW, TIFF) with disappointing results.

For instance, when using ECW format, and setting the background transparency color with Raster Design, the whole image disapears.

I've been using GlobalMapper to convert the image into different formats from the original tile raster catalog. I've also tried ArcGIS but I've found Global Mapper easier to handle.

Must add that this all started as the original tiled rasters wouldn't print when the ucs was not placed orthogonaly to the pixel orientation. After some research I thought I had find the culprit as being the compression JPEG in a TIFF file (JPEG-inTIFF). But I've tried exporting a whole image to this format and it printed.

Best regards.

[458321]

Hi @Anonymous,

It can happen that even when you set the transparency of an object, it does not seem to change how it is displayed on the screen.  This can happen if the TRANSPARENCYDISPLAY System Variable is set to 0, to not display object transparency.  Set the TRANSPARENCYDISPLAY to 1 or turn Transparency on from the Status Bar.

Other alternative solutions to try would be enabling Hardware Acceleration, or using the IMAGEADJUST and Fade.

Best regards,

Deron

[Anonymous]

Hi Deron,

Thank you for the fast reply 

We checked all the variable you mention and enabled/disabled hardware acceleration prior to publishing our post. After various tests, we confirmed that opening the exact same file (stored in our company network) will show the image either with background – in computers with Raster design installed– or with the background transparent – in computers with no raster Design installed.

The file was originally placed with the insert command of Raster Design and, in the computer where this operation was made, the image still shows with an opaque background. This different in display arose when the file was opened in a computer with AutoCAD LT and showed the transparent background instantly.

Apparently, AutoCAD alone (no Raster design installed) reads the image as “just an image” as it reads the background the same way other software, like Photoshop, do. I believe it has something to do with reading the alpha channel.

Unfortunately Raster Design seems to ignore the TIF native “background” information present in the file and, instead, just uses its own. We’ve tried PNG format and wit works fine except it’s not georeferenced.

We’ve managed to work around this by setting the background color of the TIF file to transparent with Raster Design. However, this means that every white pixel becomes transparent which is strange when the image is over a Map (We’ve tried with black background as well with the same results with black pixels).

Finally, we tried exporting a new image from ArcGIS with the background (NoData pixels) set to a color which didn´t appear in any other pixel (pink RGB 255,000,255). Inserting the image with raster design and setting this color to transparent somehow resulted but the interface between the pure pink pixels and the image showed a line of pink pixels all around the image.

We then edited the image with the pink background in Photoshop, removing all the pixels with this color and preserving the TFW file. Rebuild pyramids was necessary.

After reinserting the georeferenced TIF with Raster Design we selected the background color (at this point it was shown as black but the image has it defined as alpha channel I believe) and set it as transparent.

Now the file shows background transparency only in the area we want and the white/black pixels inside the interested area are still opaque as intended. The file behaves in the same way in every computer we’ve tested, so the problem is solved.

However, we’re not yet capable of understanding why computers with or without Raster Design show the same file (and the variables set the same way) in different way.

Best regards

Luis