I am asked to set some photos to 1000 pixel in order to make them smaller using the Irfan View program, but the program only accepts in megapixels. So, how many megapixels is 1000 pixel??
Technically, 1000 pixels would be 0,001 megapixels. But that's probably not what was intended. 1000 pixels probably refers to the image width and height, whereas megapixels usually refer to area, which is the product of width and height. You might need to clarify what exactly was meant, but I guess you should resize the images so that neither width nor height exceeds 1000 pixels.
To how many megapixels this equates depends on the picture's aspect ratio.
- If the pictures are squared, 1000 pixels times 1000 pixels is exactly 1 megapixel.
- If they are wider than high, you should resize them to 1000 pixels in width. Then, calculate the corresponding height:
(original height / original width) * 1000. The total area then is
new height * 1000 = (original height / original width) * 1000 * 1000, which makes
(original height / original width)megapixels.
- If they are higher than wide, to it the other way round. You end up with
(orignial width / orginal heigth)megapixels.
However, you're almost certainly doing the wrong thing here. Megapixels are generally refers to the total number of pixels in an image, whereas a measurement like "1000 pixels" generally refers to one dimension of the image. An image with a long dimension of "1000 pixels" and a 4:3 aspect ratio (typical of smartphones) would be 1000 x 750 pixels = 750,000 pixels = 0.75 megapixels. You need to find out what you're actually be asked to do, and make sure you're doing that.