Go to Image > Image Size and type numbers or choose Percentage and type percentage in Height or Width fields at top of Image Size window.
image-Image Size
You can do that from Edit > Content Aware Scale or from Image > Image Size.
As usual, Image > Image Size but pay attention on image resolution.
IrfanView is only available for the Windows operating system and will not work with Mac OS X. All image handling software can change the size of an image. The Mac's Preview application (in the Applications folder) can be used to open the image, and from the Tools menu select Adjust Size... to adjust the size of the image. If the image is in the Mac's iPhoto library you can Export from the library (from iPhoto's File menu) and change the size as required. All other image editing software will offer similar size changing options.
That depend on resolution. Open image in Photoshop and go to Image > Image Size. Pixel dimensions you can see on the top of Image Size window.
The larger the resolution, the larger the file size. When you compress a photo, chances are you are going to lose a lot of information from the photo that degrades picture quality.
You can enlarge image in Image Size dialog in Photoshop, Image > Image Size. At top of window you will see current/new size in bytes. When you enlarging images be aware because you can loose quality.
Click on Image on the menu, then select Image Size and type in the sizes you want.
You can do that with Crop tool or from Image -> Image Size. See ralated link for good explanation how to do that properly.
That depends on who the photographer was, how many copies of the image are in circulation, the size and condition of the photo, etc.
First You open your photo in image ready software then you reduce your size as you want and then save this photo with save optimized as option and check the size of photo. In this way you reduce your size of photo with particular way. If the size is not convert as your want you reduce the image size again and again save this photo with save optimized option. In this way you will surely convert in specific size.Note : The save optimized option is available in File Menu.
The average scanning speed for an automatic photo scanner depends on the size of the image and whether or not the image is colour or black and white. Time can vary from 16 seconds to 30 seconds.