I am using react-native-photo-view-ex library to zoom in and out the images. After zooming the image I am getting scale size from onScale callback function.After than I saved this picture and when I want to open saved image again for re-edit with same scale size as I saved the image displayed very small.I adjust minZoom = 0.5 and maxZoom = 10.
This code works perfectly in android and when open images for re-edit in android image displayed on accurate position with given scale. Also I have implemented this feature with gesture handler and ScrollView Zoomable but get same results. Can anyone help me?
<PhotoView
source={{uri: selectedData.url}}
scale={imageScale}
minimumZoomScale={0.5}
maximumZoomScale={10}
onScale={e => {
setImage(e.nativeEvent.scale);
}}
onLoad={() => setImageScale(selectedData.scale, false)}
style={
styles.resizeImageWrapper
}
/>
Related
I want modify the contrast, sharpness, etc. of images. I am testing that with react-native-color-matrix-image-filters which seems to work fine. But I am not sure how to save the resulting images to the camera roll or how to get the base64 result. The following code will convert the original image to a greyscale image. How can I save the result?
import {
Grayscale,
Sepia,
Tint,
ColorMatrix,
concatColorMatrices,
invert,
contrast,
saturate
} from 'react-native-color-matrix-image-filters'
<View>
<Grayscale>
<Image style={styles.imgstyle}
source={{
uri: sourceImage,
}}
/>
</Grayscale>
</View>
These module doesn't support save images (see here), you can use a combination of this module or react-native-image-filter-kit (for filters) and https://github.com/gre/react-native-view-shot to be able to download the image from your app
I have a react native project built on expo.
I need to view an image on screen with a style that is based on the width and height of that image.
How can I get the width and height of that image?
let's say the image uri is file:///storage/emulated/0/WhatsApp/Media/WhatsApp%20Images/IMG-20200117-WA0019.jpg
A solution with a code sample is highly appreciated..
React Native Image provide getSize() to get the size of remote images.
Image.getSize('uri', (width, height) => {
this.setState({ width, height });
});
For local images you can use resolveAssetSource()
Image.resolveAssetSource(source).width
Image.resolveAssetSource(source).height
Hope this helps you. Feel free for doubts.
I want to display a loader image till my image is loaded to the react-native Image. Back is an image which is stored locally and it has been imported to the screen.
This code gives me a blank screen for 'Back' image. When I set the source as source={Back} it works. But the following doesn't work. What am I doing wrong here?
<View style={styles.imageWrapper}>
<NonClickableImage
source={this.state.loaded ? Back : {uri: detailedMovement.image}}
resizeMode="stretch"
width={width - 20}
height={200}
onLoad={() => this._onMovementImageLoaded()}
/>
</View>
I think your logic needs to be:
{!this.state.loaded ? Back : {uri: detailedMovement.image}}
Because you want to show the Back icon when the state is NOT loaded. Currently, if the state is loaded, then you display Back.
I've built a React Native iOS app which is fairly basic; it's a few screens which the user can click through to from a 'Home' component, and each one consists of basic components comprising solely Text/View/Image components.
In simulator the app is responsive and there aren't any JS console warnings, however when I do a release to my iPad (Air 2), there's a noticable lag between the home screen and certain other screens. These are notably the screens which have more images on.
I'm wondering if it's because I'm using larger images (the app was designed for the iPad Pro 2) and scaling the images down for use where I want them. The worst offender is a page which has a masonry-style grid of images. There's still only about 30 in a ScrollView there though. Once the component has been shown once the app is much more responsive.
I've already taken steps to optimise my components in terms of using extending PureComponent or using stateless functions wherever possible, and console logging shows me that the touchables are responding immediately, so the delay is definitely at the render time of the component.
N.B. All images are local (loaded via require('./path/to/file')), nothing is being loaded over the network.
Here's an example of the code that populates an array of items for display inside the ScrollView:
...
const items = mediaItems.map((item, index) => {
// scale desired width (1044 for video, 520 for images) based on designed width and device aspect ratio.
const imageWidth = item.video ? (1044/2732) * deviceWidth : (520/2732) * deviceWidth
return (
<TouchableHighlight key={index} onPress={() => onOpen(item)}>
<View style={[styles.gridImageView, { width: imageWidth }]}>
<Image style={styles.gridImage} source={item.image} />
</View>
</TouchableHighlight>
)
});
...
and the styles for the gridImageView and gridImage are as follows:
...
gridImageView: {
height: (460/2732) * width,
margin: (2/2732) * width,
position: 'relative'
},
gridImage: {
resizeMode: 'cover',
width: null,
height: null,
flex: 1,
alignItems: 'center',
justifyContent: 'center'
},
...
So my question is kind of multi-layered:
What is the best practice with regards to ensuring the component appears quickly?
Should I not be setting a width/height on the image itself at all?
Should I be doing some kind of pre-loading of the images in the sizes I want before I let the user begin to navigate around the app?
Should I be using JPG instead of PNG images?
Is there another trick I'm missing?
Should I not be setting a width/height on the image itself at all
You have to set a width and height. If you don‘t do so, your image won‘t display
Should I be doing some kind of pre-loading of the images in the sizes I want before I let the user begin to navigate around the app?
It is a good idea to downlod images beforehand. Huge images need a lot of performance. Probably your issues are gone, if you resize your images before displaying them. Therefore you could use react native image resizer
Should I be using JPG instead of PNG images?
You should use JPGs, because they provide a higher compression rate.
Consider this simple ScrollView.
On iOS, clicking on the text will but the text to the top because scrollTo({ y: 250 }) scrolls even if end of scrollView is reached.
On Android, the text doesn't move.
How to get on Android the same behavior we have on iOS?
You can work around this by adding padding to the contentContainerStyle of the ScrollView. A good starting point would be to add padding equal to the height of the device's screen.
import { Dimensions } from 'react-native';
const ANDROID_SCREEN_HEIGHT_PADDING = Dimensions.get('window').height;
then, when rendering:
<ScrollView
contentContainerStyle={{paddingBottom: ANDROID_SCREEN_HEIGHT_PADDING}}>
...
</ScrollView>
You could use this for necessary extra Android padding in every direction. If you are using horizontal={true}, for example, you could add padding equal to the width of the screen and add it to the paddingLeft style property to get the intended scrolling behavior on Android.
This behavior is due to the underlying implementation of ScrollView on Android in React-Native. See also:
React native Android ScrollView scrollTo not working