Raster image background white

[archbaech]

  I have a a graphic image from a client to use as signage on my 3d model. In photoshop I have isolated the letters and the logo only by erasing the background. No color is in the background, not white nor black, it is transparent in Photoshop.

  I saved the image as a .jpg, .tif .tga. and .bmp.  Any of these raster images, when inserted into the drawing, shows the background as white.   I cannot undertsand how to make it transparent so it looks like letters painted on the wall.

 I have changed IMAGEFRAME set to 0 - no change,  I have set properties TRANSPARENCY to YES but no change.

Am I missing a step, or does the program always show raster images in a box?

ACA 2009

[jmcintyre]

Autocad does not recognise transparent backgrounds to images.

You can create a closed polyline and xclip the image.

[aghis_no · Accepted solution]

Autocad Does support transparency.

You have to have what is called an "alpha channel" in your image in order to have transparent background in Autocad.

To do so: in Photoshop, when you erase your background you have to hover over the layer icon (on the layer window) hold down the control key and left click on it in order to select the  layers opacity. (You will notice that when over the icon and with the control key pressed, the hand cursor will have a small selection rectangle next to it). With the selection active, you have to switch to the Channels window, where you will find right down at the bottom frame of the window the button "save selection as channel". By pressing this (while the selection is active) you will create a new channel called "Alpha 1". This new channel will be a black and white image representing as black the background that you wish transparent, and white the opaque part of the image. Then you just have to save your image on a file format that supports alpha channels PNG, TIFF, TGA, but not JPG. PNG is the best because it is smaller than TIFF.

Then inside AutoCAD or any other AutoCAD vertical program (ADT/ACA) you have to activate the transparency option for the image. I send you exmpale of a PNG file with an aplha channel. just try it in Autocad it works.

hope this helps

regards

aghis

[BoleMo]

This is an old post but just wanted to thank you for such great explanation...just saved me hours of research...

Rookie

[MichaelBussiere2]

Great work Aghis, and thank you for your contributions in the community to help users overcome this issue with raster images.