File Compression or Jsut File Size

[sullyn]

Hi Just installed and tried to open a 712KB tiff image and got the out of memory message so tried to open a 187KB tiff which opened Ok but when I saved it again with out any changes it is 2,145KB. It this because Paint.Net does not support compression or is there another reason? I currently have 4GB of ram installed.

Regards

Neil

[david.atwell]

Here's Rick's explanation, from another thread:

Paint.NET's architecture is such that it must:

1) Hold the entire image in memory

2) Have a bitmap used for compositing the image

3) Have a scratch surface

(3) is not always in use, but it's important to have it allocated because it makes error handling much simpler. If you clicked on the Clone Stamp and suddenly got an out of memory error, that would be lame. (2) is not always important, as a single layer image effectively needs no compositing.

So, to compute the memory requirements for an image, the following formula can be used:

(W x H x 4) x (L + 2)

W is the width of the image in pixels, H is the height in pixels, 4 is because each pixel takes 4 bytes, L is the number of layers, and the +2 accounts for (2) and (3) above.

So for your 7680x2880 image, which I assume has 1 layer, the total memory required is:

(7680 x 2880 x 4) x (1 + 2)

= (88473600) x (3)

= 265,420,800

= 253.125 MB RAM

When you resize an image, you must have enough memory to hold the image at both its old and new sizes. Other factors influence how much memory is available. For instance, just because there is still 1 GB of virtual address space available does not mean that there is 1 GB available contiguously.

Programs like Photoshop and The GIMP have complicated memory managers that tile the image, swapping it out to scratch pads (disk) as necessary. This impacts coding complexity because every part of the application that works with the image must take the tiling in to consideration. It also affects performance, but has the advantage of being able to work with much larger images. For Paint.NET, I purposely chose a design that enabled coding simplicity for many reasons.

If you have a 64-bit CPU and OS, you will have a much harder time running out of memory. You may also look into the /3GB switch for the boot.ini file, although I do not know for sure that this will help: http://support.microsoft.com/default.as ... E05B0ABAAA