What image size should I ask from UI developer?

Question

I have an ImageView with these attributes:

   android:layout_width="match_parent"
   android:layout_height="160dp"

UI developer asks me for the size of Image that I want in px. What size should I ask? Should I ask different size for different devices?

Note

I don't have an ImageView with specific height and width. My ImageView width is match_parent not a specific width.

All the answers say that I should use a converter, How can I convert match_parent to px?

According to answers, I should ask about six images, shouldn't I?

Answer 1

You should give highest screen density in pixels to your UI developer then scale to lower densities on your own.

Normally an android app will support screen densities ldpi at min and xxxhdpi at max.

Step1: If you want the image size is 160 x 160 dp then give the UI developer the highest image size associated with max screen density.

160 x 4 = 640x640 px (why multiply by 4? I will explain later)

Step 2: Scale the image 640x640 px to lower size based on screen densities

• ldpi: 160 x 0.75 = 120x120 px
• mdpi: 160 x 1 = 160x160 px
• hdpi: 160 x 1.5 = 240x240 px
• xhdpi: 160 x 2 = 320x320 px
• xxhdpi: 160 x 3 = 480x480 px
• xxxhdpi: 160 x 4 = 640x640 px

Tips: Find your image size corresponds with mdpi density screen (known as base density or 1X density) then scale to other densities by the following formula

Update: From https://material.io/tools/devices/, screen size for base density screen is 360x640 px. So your ImageView size will be 360x160 px on 1X density screen.

ldpi: 270x120 px 
mdpi: 360x160 px
hdpi: 540x240 px
xhdpi: 720x320 px
xxhdpi: 1280x480 px
xxxhdpi: 1440x640 px

Answer 2

Why are you not using Vector drawable?

Why use Vectors?

1. Data can be represented in original resolution without generalization.
2. Graphical outputs of the images are more pleasing than the created as raster image
3. Another very important reason of using vector graphics rather than raster is their size. Vector objects are much smaller than raster image format. If we have the full-size image to update, the vector file might only take few kilobytes of space on your system, where the same image in medium resolution bitmap format might not place on CD ROM.

You should use SVG images in your project.

Create SVG instead of PNG files