hi, i have a little problem with blue prints when i have all images the same size but when i make a box to check if its right the top and front view doesnt match but its the same size image how can i make it good?
see attactments for screenshot of problem
thank you,
tinyq
First, check out the axes. In the side view, y points toward the rear of the tank, in the top view y points toward the side and x points toward the back. You’ll need to sort that out by rotating the images in Gimp, Photoshop, Irfanview or your choice of external 2d image programs.
Second, when you place background images, you can adjust the size of the image, which will allow you to match the image to the overall size of your mesh box. This may not work perfectly, usually because the blueprint images have scaling or distortion along an axis, or simply were poorly drawn in the first place. But you can get pretty close.
I’d also recommend getting photographs at different angles, sometimes they can clear up what’s going on when the blueprints are ambiguous.
Good luck, and Welcome to BlenderArtists 
thank you for your welcome:D
i have another problem the blueprints have the same size and its has the same width and hight 116*266 pixels but the picture of the side view is too small again how can i slove this problem?
tinyq: where did you get these blueprints?
and you should be able to increase the size by raising the “Size” slider in the floating “Background Image” panel.
Press “View Name”
it will help you to know on what view you are
The pixel size of the blueprint images is fairly irrelevant, the key is whether you can match the drawings to a rectangular prism.
Make the rectangle match x and y in the top view. Then move to the side view and resize the image until the length matches (you can’t see the x axis) then scale the rectangle along the z axis until the height matches the resized image. Then go into the front view and resize the image there to match the height. If the drawings are well drawn, the width in the front view should also match, with no more adjustments.
Note: resizing images scales the whole image, you can’t selectively stretch the image to match only one dimension. If this is a problem, you’ll have to modify the poorly drawn image in another program, such as the gimp or photoshop.
A trick I learned…
Open up all your images in the gimp (or photoshop if you’re wealthy) as separate layers and make them all the same relative size and match up with each other. It helps a lot if you make the center of whatever you’re modeling the center of the image as well.
Once you have everything lined up make the image a square and pad out all the layers (I fill the new areas with the background color) and then save all the layers as separate images.
Now you should be able to use the background image in blender without having to go through all the hassle of resizing and moving it around.
Blender uses one bu as the image size so it changes the relative size of the image.
