Speaking from the realization of a design, why under the simulator resolution is 375 ip6 and general design to 750?
Look above this figure, the first screen size is the actual physical dimensions , with emphasis on the resolution and the resolution pt px, To answer this question, we must understand pt and px. Pt So what is it? pt also called logical resolution, simple to understand will be appreciated that units of length. He only has a relationship and screen size, 3 and 4 are 320pt. 5 Why is 320pt it? Because of the height, so a little more size. But his logic is the width of resolution 320. So he simply understood that the size of the screen has a relationship with pt. He is a unit of length .
So px is what concept? We told him to be called
physical resolution. He and screen size has nothing to do
, he is not a visual unit. Simply, a pixel can be understood. We saw pictures are made up of many dots of pixels. Why he is not related to the length of a unit it? We can only describe how many points can not be described in much the point.
So it can get
a relationship pt and px, is a pt, there are several px. Or there can be a number pt px included
. So why screen effect of 4 to 3 better? This is the number of pixels a physical resolution of which contains the logical relationship. 3 and 4 logical resolution is 320 * 480. The key is that they are not the same physical resolution. 4 corresponds to 960.3 * 640 * 480 320 corresponds. The same length, 3 less than half.
So Reader Here is 1 times, 2 times the relationship. What does this indicate? This represents the same pt below contains a number of px. The more we following the same unit, the physical point, the displayed image more delicate, more clear. 6plus 3 times. Per unit below a ratio of more than 6 pixels. Theoretically clearer. But the human eye can not be seen, is already twice the limit of the human eye can distinguish.
Finally, this ppi. ppi What is the concept, the concept he and Reader are the same. Reader mean how many of each pt px included below.
ppi contains every inch represents the number of physical pixels
. So this is how 163 get out. 3.5-inch diagonal represents the distance, the distance diagonal know, how that beg the 163, that is, the Pythagorean theorem, 320 * 480 divided by the square root square 3.5-inch get.
Therefore, the designer is given according to the physical resolution, not according to the logical resolution. 6 it is below 2 times relationship.
to sum up:
1, pt also called logical resolution
2, pt screen size and the size relationship will be appreciated that the length and simple visual units
3, px refers to the physical resolution, and screen size does not matter. Because the point of no size, only how many.
A, pt 1 can have a configuration px, there may be two, it may also be composed of three or more.
b, ip6 next two px constitutes 1 pt.
rpx role