Raster Image Questions

[nicolas]

Hi,

 

I have some issues with Raster Image lately when I wanted a scanned jpeg of 210 x 297 mm (a4 dimension) that I want to fit into a 180x220 mm rectangular box in Autocad. I have used Photoshop CS 3 to change the image size to 180x220.

 

However when I insert the Raster Image files, some files are automatically set to 180x220 (as expected) and others are scaled down and I have to re-scale them (reset the scale value to 1, change the x-value and the y-value is automatically changed, but on the overall it is 180x220, sometimes x is more than y or sometimes y is more than x, but within 1-3 mm)

 

I want to know :

 

1. What is the best principle or techniques of knowing/changing image dimension (mm)

2. How to be able to scale raster image in x-axis and y-axis independently of one another?

3. Remove white background to neutral background?

 

Thank you in advanced,

 

Regards,

 

Nicolas.

[CyberAngel]

The best way I have found to use images in a drawing is to make sure there is a scale or scalable object in the image. Once you insert the image, measure the distance along the scale or object. Divide the actual scale distance by the measurement. Change the image's scale by that ratio. It helps to use a round number as the original scale, e.g. 1, 100, 1000.

 

As far as I know, you can't independently change the x and y scales of an inserted image. You can, however, adjust them in the source image. Image processors will usually let you adjust the image size.

 

Again, you will have to use your image processor. If you have a "background" color, you can use a color fill or color change command to replace white with background. I don't know if that carries through to AutoCAD, but it should.

[nicolas]

Hi,

 

Thank you for answering. I believe there must be a way to actually do the scaling of raster image. I will have to dig deeper. Meanwhile I have tried to print the image in monochrome, none, grayscale and change values of transparency to yes and no, clipped image to yes and no and nothing to no avail. In Photoshop, I can delete the white background but as soon as I save the image to jpeg or any other format, the white background automatically appears. I believe this has to do with one Autocad 2011, Autocad 2012 settings because as I checked in old catalogues done by predecessors in older versions of Autocad, there were no background in their printing. Clear images.

 

I have attached one of the inserted raster image properties.

 

Regards,

 

Nicolas.

 

[eldon]

As a work around, have you tried making a block of your raster image, then you can insert it at differing X and Y scaling.

 

Tiff images can support transparency, but the only way I can get them to work is to scan a printed image to get the Black and White Tiff file.

[nicolas]

Hi,

 

Regarding Background:

 

I found the answer in CADTUTOR Tutorial. I have to make the image into Bitmap. Actually all the images were converted to MODE|grayscale in Photoshop. With this, I can easily turn transparency on and off.

 

Regarding Dimension of Images:

 

I believe that making a block and including the raster image into it can be a solution as I have already done so with a logo that I've inserted successfully into a catalogue some months ago. There is an image size option in photoshop that I am using but it is not working as precisely and smoothly as expected through it is with range.

 

Regards,

 

Nicolas

[nicolas]

TURN WHITE BACKGROUND TRANSPARENT

 

Another method that I have used successfully today is to open the jpeg in paint and "save as ..." 256 Color Bitmap. Following insertion of the raster bmp drawing in Autocad, right click the image and turn transparency on. The background becomes fully transparent.

 

Regards,

 

Nicolas.