Sorry for the late reply, but I had to do research on why the pictures become so big in file size when you import them on Nextion.
The accepted picture types to import are *.jpg, *.png, non animated *.gif and *.bmp files.
When importing a picture, the picture is converted into the 565 16 bit color format used by Nextion.
In Basic and Enhanced models: Nextion is not a graphics card, as such transparency and in picture animation is not supported.
In native 16-bit color, picture, resources consume 16 bits per pixel, or width x height x 2 bytes.
In Intelligent models: Nextion now supports transparency and image compression allowing more picture resources for the same space, the 2 bytes per pixel formula does not apply.
Also, I wanted to see if this was true, so I tested it to prove it.
For Basic and Enhanced models:
| Resolution | .tft file size | format/image size | imported image size | .tft after import |
|---|---|---|---|---|
| 480x320: | 277 KB | .png / 196 KB | 307,224 B | 605,536 B |
| 480x320: | 277 KB | .jpg / 12 KB | 307,224 B | 605,536 B |
| 800x480: | 277 KB | .png / 351 KB | 768,024 B | 1064,288 B |
| 800x480: | 277 KB | .jpg / 22 KB | 768,024 B | 1064,288 B |
And for Intelligent models:
| Resolution | .tft file size | format/image size | imported image size | .tft after import |
|---|---|---|---|---|
| 800x480: | 538 KB | .png / 351 KB | 138,919 B | 669,980 B |
| 800x480: | 538 KB | .jpg / 22 KB | 88,630 B | 669,980 B |
Conclusion:
Basic and Enhanced models no matter the picture format and size, the final size of the imported image, will be the same, following the rule: width x height x 2 bytes. For example: 8004802=768,000B.
For the Intelligent models, the file format does not matter again, as the final .tft file size will be the same, following Nextion's image compression.