I currently have images which the image name is returned by a function and is dynamically called based on a variable like this:
String _setImage() {
if (currentQuestion > 1 && currentQuestion < 11) {
return "assets/images/image_$intensityIndex.png";
} else {
return "assets/images/image.png";
}
}
I want to switch to preloading the images and I am using the technique described at Preload images in a stateful widget on Flutter, but I am not sure how to have the function return an image which the name is dynamically determined based on another variable. Here is what I have so far:
void initState() {
super.initState();
image0 = Image.asset('assets/images/image_0.png');
image1 = Image.asset('assets/images/image_1.png');
image2 = Image.asset('assets/images/image_2.png');
image3 = Image.asset('assets/images/image_3.png');
}
void didChangeDependencies() {
super.didChangeDependencies();
precacheImage(image0.image, context);
precacheImage(image1.image, context);
precacheImage(image2.image, context);
precacheImage(image3.image, context);
}
Image _setImage() {
if (currentQuestion > 1 && currentQuestion < 11) {
return ______________;
} else {
return image0;
}
}
All help is appreciated!
Am not sure how to return an image which the name is dynamically
determined based on another variable
You don't need to return with precach because if you use exact image that you cache.
Ex:
precacheImage('assets/images/image_1.png'); // if this is the image name
Image.asset('assets/images/image_1.png'); // when you use this it is getting from the cache but the path should be same.
If I explain it another way:
precacheImage("assets/images/image_$intensityIndex.png"); // image_1.png
Image.asset('assets/images/image_1.png'); // when you do this, asset taking from the cache by looking at the path.
Related
I'm trying to show ads in recycleview and i succeeded to do it using the code below .. the problem is that in every "MspaceBetweenAds" position the ad show up but the article at this replaced with the ad
i tried to fix it by modifying ItemCount() by Mposts.Count + (Mposts.count% MspaceBetweenAds) but i'm getting "IndexOutOfBounds " error
any help please .. this is my code
public class AdsView : ListViewHolder
{
public AdView mAdView { get; private set; }
public AdsView(View view) : base(view)
{
mAdView = view.FindViewById<AdView>(Resource.Id.AdsCard);
}
}
public override RecyclerView.ViewHolder OnCreateViewHolder(ViewGroup parent, int viewType)
{
RecyclerView.ViewHolder vh = null;
switch (viewType)
{
case 1:
View vBig = LayoutInflater.From(parent.Context).Inflate(Resource.Layout.BigCard, parent, false);
vh = new MyView(vBig);
break;
case 2:
View vAds = LayoutInflater.From(parent.Context).Inflate(Resource.Layout.AdsCard, parent, false);
vh = new AdsView(vAds);
break;
}
return vh;
}
public override void OnBindListViewHolder(ListViewHolder holder, int position)
{
var MyHolder = holder as MyView;
switch (holder.ItemViewType)
{
case 1:
// code to show posts articles here
break;
case 2:
var AdHolder = holder as AdsView;
fnc.AddBannerAd(AdHolder.mAdView);
break;
}
}
public override int GetItemViewType(int position)
{
if (position > 0 && position % mSpaceBetweenAds == 0) { return 2; }
else { return 1; }
}
and this is a demo app https://drive.google.com/open?id=1Tk3G8dw9nqIffxmEFNGqIgXNzCJJPxD_
As the demo you posted contains 3rd party package, I cannot run it directly and modify the demo for you. The flowing is my solution to your problem:
Error causes:
The way you do (modifying ItemCount() by Mposts.Count + (Mposts.count% MspaceBetweenAds) cannot change the real length of Mposts, as a result, it results in the
"IndexOutOfBounds " error.
Solution
If you want to insert ads into your recylerview, you need not only modify your adapter to show both item and ads, but also need to modify your layout resource file, that is, you need to insert the ads data into the data list for of your recylerview. Or you can simply add a duplicated item to the list every [MspaceBetweenAds]items.
UPDATE: The initial question has been answered as to why the crashes happen but the lingering problem remains of why is the 'OnImageAvailable' callback called so may times? When it is called, I want to do stuff with the image, but whatever method I run at that time is called many times. Is this the wrong place to be using the resulting image?
I am using the sample code found here for a Xamarin Android implementation of the Android Camera2 API. My issue is that when the capture button is pressed a single time, the OnCameraAvalibleListener's OnImageAvailable callback gets called multiple times.
This is causing a problem because the image from AcquireNextImage needs to be closed before another can be used, but close is not called until the Run method of the ImageSaver class as seen below.
This causes these 2 errors:
Unable to acquire a buffer item, very likely client tried to acquire
more than maxImages buffers
AND
maxImages (2) has already been acquired, call #close before acquiring
more.
The max image is set to 2 by default, but setting it to 1 does not help. How do I prevent the callback from being called twice?
public void OnImageAvailable(ImageReader reader)
{
var image = reader.AcquireNextImage();
owner.mBackgroundHandler.Post(new ImageSaver(image, file));
}
// Saves a JPEG {#link Image} into the specified {#link File}.
private class ImageSaver : Java.Lang.Object, IRunnable
{
// The JPEG image
private Image mImage;
// The file we save the image into.
private File mFile;
public ImageSaver(Image image, File file)
{
if (image == null)
throw new System.ArgumentNullException("image");
if (file == null)
throw new System.ArgumentNullException("file");
mImage = image;
mFile = file;
}
public void Run()
{
ByteBuffer buffer = mImage.GetPlanes()[0].Buffer;
byte[] bytes = new byte[buffer.Remaining()];
buffer.Get(bytes);
using (var output = new FileOutputStream(mFile))
{
try
{
output.Write(bytes);
}
catch (IOException e)
{
e.PrintStackTrace();
}
finally
{
mImage.Close();
}
}
}
}
The method OnImageAvailable can be called again as soon as you leave it if there is another picture in the pipeline.
I would recommend calling Close in the same method you are calling AcquireNextImage. So, if you choose to get the image directly from that callback, then you have to call Close in there as well.
One solution involved grabbing the image in that method and close it right away.
public void OnImageAvailable(ImageReader reader)
{
var image = reader.AcquireNextImage();
try
{
ByteBuffer buffer = mImage.GetPlanes()[0].Buffer;
byte[] bytes = new byte[buffer.Remaining()];
buffer.Get(bytes);
// I am not sure where you get the file instance but it is not important.
owner.mBackgroundHandler.Post(new ImageSaver(bytes, file));
}
finally
{
image.Close();
}
}
The ImageSaver would be modified to accept the byte array as first parameter in the constructor:
public ImageSaver(byte[] bytes, File file)
{
if (bytes == null)
throw new System.ArgumentNullException("bytes");
if (file == null)
throw new System.ArgumentNullException("file");
mBytes = bytes;
mFile = file;
}
The major downside of this solution is the risk of putting a lot of pressure on the memory as you basically save the images in memory until they are processed, one after another.
Another solution consists in acquiring the image on the background thread instead.
public void OnImageAvailable(ImageReader reader)
{
// Again, I am not sure where you get the file instance but it is not important.
owner.mBackgroundHandler.Post(new ImageSaver(reader, file));
}
This solution is less intensive on the memory; but you might have to increase the maximum number of images from 2 to something higher depending on your needs. Again, the ImageSaver's constructor needs to be modified to accept an ImageReader as a parameter:
public ImageSaver(ImageReader imageReader, File file)
{
if (imageReader == null)
throw new System.ArgumentNullException("imageReader");
if (file == null)
throw new System.ArgumentNullException("file");
mImageReader = imageReader;
mFile = file;
}
Now the Run method would have the responsibility of acquiring and releasing the Image:
public void Run()
{
Image image = mImageReader.AcquireNextImage();
try
{
ByteBuffer buffer = image.GetPlanes()[0].Buffer;
byte[] bytes = new byte[buffer.Remaining()];
buffer.Get(bytes);
using (var output = new FileOutputStream(mFile))
{
try
{
output.Write(bytes);
}
catch (IOException e)
{
e.PrintStackTrace();
}
}
}
finally
{
image?.Close();
}
}
I too facing this issue for longer time and tried implementing #kzrytof's solution but didn't helped well as expected but found the way to get the onImageAvailable to execute once.,
Scenario: When the image is available then the onImageAvailable method is called right?
so, What I did is after closing the image using image.close(); I called the imagereader.setonImageAvailableListener() and made the listener = null. this way I stopped the execution for second time.,
I know, that your question is for xamarin and my below code is in native android java but the method and functionalities are same, so try once:
#Override
public void onImageAvailable(ImageReader reader) {
final Image image=imageReader.acquireLatestImage();
try {
if (image != null) {
Image.Plane[] planes = image.getPlanes();
ByteBuffer buffer = planes[0].getBuffer();
int pixelStride = planes[0].getPixelStride();
int rowStride = planes[0].getRowStride();
int rowPadding = rowStride - pixelStride * width;
int bitmapWidth = width + rowPadding / pixelStride;
if (latestBitmap == null ||
latestBitmap.getWidth() != bitmapWidth ||
latestBitmap.getHeight() != height) {
if (latestBitmap != null) {
latestBitmap.recycle();
}
}
latestBitmap.copyPixelsFromBuffer(buffer);
}
}
catch(Exception e){
}
finally{
image.close();
imageReader.setOnImageAvailableListener(null, svc.getHandler());
}
// next steps to save the image
}
I have a pdf which contains a lot of invisible paths. Since the amount of path produces problems later on, I would like to remove the ones that have white colors.
So far I am trying to do this with a ContentScanner:
public class FilterWhitePathScanner implements Scanner {
private static final Logger LOG = LoggerFactory.getLogger(FilterWhitePathScanner.class);
private int count = 0;
public void scan(ContentScanner level) {
if (level == null)
return;
while (level.moveNext()) {
ContentObject object = level.getCurrent();
if (object instanceof ContainerObject) {
// Scan the inner level!
scan(level.getChildLevel());
} else if (object instanceof org.pdfclown.documents.contents.objects.Path) {
AffineTransform ctm = level.getState().getCtm();
Color<?> strokeColor = level.getState().getStrokeColor();
Color<?> fillColor = level.getState().getFillColor();
if (checkWhite(fillColor) && checkWhite(strokeColor)) {
level.remove();
} else {
LOG.info("Stroke Color " + strokeColor + " - Fill Color " + fillColor);
}
} else {
LOG.info("Object:" + object);
}
}
}
It recognizes the paths correctly, but in the end these are not removed from the PDF. Here the code handling the PDF (it extracts only one page from the source pdf):
Document targetDoc = new File().getDocument();
targetDoc.getPages().add(sourceDoc.getPages().get(pageNum).clone(targetDoc));
Page page = targetDoc.getPages().get(0);
Contents contents = page.getContents();
FilterWhitePathScanner filterWhitePathScanner = new FilterWhitePathScanner();
filterWhitePathScanner.scan(new ContentScanner(contents));
LOG.info("White Paths: " + filterWhitePathScanner.getCount());
targetDoc.getFile().save(tempFilePath.toFile(), SerializationModeEnum.Standard);
The saved PDF file still contains the paths I tried to remove. How can I remove objects from the PDF finally?
Thanks,
Thomas
Finally found the solution in the Java doc:
You have to call contents.flush(); to persist the changes into the pdf file.
So I added this line to the PDF handling code before calling save and it works!
I try to pick an image from sdcard and then crop it.
ACTION_PICK is OK, but when i call ACTION_CROP, my system gallery app (I call it as A) can't done the action, but another app (B) can.
I tried the following cases:
1/ Pick by A and then crop by A => pick OK, crop fail
2/ Pick by B and then crop by A => the same as first case.
3/ Pick by A and then crop by B => every things OK.
4/ Pick by B and then crop by B => every things OK.
So my temporary conclusion is: my system app can't do the crop action with my code (may be i forgot something). Here is my code:
ACTION_PICK:
public Intent galleryIntent() {
Intent galleryIntent = new Intent(Intent.ACTION_PICK);
galleryIntent.setType("image/*");
galleryIntent.putExtra("return-data", true);
return galleryIntent;
}
ACTION_CROP:
public Intent cropIntent(Uri inUri, int outputX, int outputY,
boolean isScale) {
Intent cropIntent = new Intent("com.android.camera.action.CROP");
cropIntent.setDataAndType(inUri, "image/*");
cropIntent.putExtra("crop", "true");
cropIntent.putExtra("aspectX", outputX);
cropIntent.putExtra("aspectY", outputY);
cropIntent.putExtra("outputX", outputX);
cropIntent.putExtra("outputY", outputY);
cropIntent.putExtra("scale", isScale);
cropIntent.putExtra("return-data", true);
return cropIntent;
}
My onActivityResult method
#Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
if (resultCode == RESULT_OK) {
switch (requestCode) {
case REQUEST_CODE_GALLERY:
imageUri = data.getData();
startActivityForResult(cropIntent(imageUri,
500, 500, true), REQUEST_CODE_CROP);
break;
case REQUEST_CODE_CROP:
Bundle extras = data.getExtras();
Bitmap tempBitmap = extras.getParcelable("data");
imgvMain.setImageBitmap(null);
imgvMain.setImageBitmap(tempBitmap);
break;
}
} else {
imageUri = null;
}
}
Am i missing somethings?
Thank for your attention!
I use this code successfully for Android 2.2 and up:
It opens a selection of apps that can get image files e.g. the Gallery app. If the selected app can crop, it will also do so.
The cropped image will be saved to the supplied temp file.
(note the small difference for KITKAT).
Intent intent = new Intent();
intent.setType("image/*");
intent.putExtra("crop", "true");
intent.putExtra("outputX", Constants.IMAGE_WIDTH);
intent.putExtra("outputY", Constants.IMAGE_HEIGHT);
intent.putExtra("aspectX", 1);
intent.putExtra("aspectY", 1);
intent.putExtra("scale", true);
intent.putExtra("scaleUpIfNeeded", true);
intent.putExtra(MediaStore.EXTRA_OUTPUT, Uri.fromFile(<a temp file created somewhere>));
intent.putExtra("outputFormat", Bitmap.CompressFormat.PNG.toString());
if (Build.VERSION.SDK_INT < Build.VERSION_CODES.KITKAT)
{
intent.setAction(Intent.ACTION_GET_CONTENT);
}
else
{
intent.setAction(Intent.ACTION_PICK);
intent.setData(android.provider.MediaStore.Images.Media.EXTERNAL_CONTENT_URI);
}
startActivityForResult(intent, RESULT_CROP);
EDIT:
I ended up using custom cropping using: https://github.com/biokys/cropimage. It was very easy and I had no more troubles with cropping :-)
I checked the logs by filtering with gallery3d and found out that the stock app is not getting permission to access the uri. Hence it's behaving unexpectedly. That behaviour is different for different platforms.
Solution:
get the uri of the selected image in onActivityResult() for intent ACTION_PICK.
save the image temporarily.
create new URI from the saved image.
pass the new URI to com.android.camera.action.CROP.
Sample code: (Dont copy paste. for simplicity ,I have removed the error checks and async tasks.)
public void pickCroppedPhoto(){
Intent photoPickerIntent = new Intent(Intent.ACTION_PICK);
photoPickerIntent.setType("image/*");
photoPickerIntent.putExtra("crop", "true");
populateCropExtras(activity, photoPickerIntent);
startActivityForResult(photoPickerIntent , REQUEST_CODE_PICK);
}
#Override
protected void onActivityResult(int requestCode, int resultCode, final Intent data) {
if (requestCode == REQUEST_CODE_PICK ) {
File mainImage = saveUriInFile( this,
data.getData(),
getTempFileForMainImage());
if (null == mainImage) {
handleImageSelectionFailure();
}else {
try {
Uri mainFileUri = Uri.fromFile(mainImage);
performCrop(this,mainFileUri);
}catch(Exception e){
handleImageSelectionFailure();
}
}
}else if ( requestCode == PIC_CROP ){
postImageSelection(data.getData());
}
}
Here is my performCrop code which is similar to that of the question.
public static boolean performCrop(Activity activity, Uri picUri) {
try {
Intent cropIntent = new Intent("com.android.camera.action.CROP");
// indicate image type and Uri
cropIntent.setDataAndType(picUri, "image/*");
if (populateCropExtras(activity, cropIntent)) return false;
activity.startActivityForResult(cropIntent, PIC_CROP);
return true;
}
// respond to users whose devices do not support the crop action
catch (ActivityNotFoundException anfe) {
String errorMessage = "Device doesn't support crop!";
Log.w(PhotoPickerUtil.class.getCanonicalName(), errorMessage);
return false;
}catch (IOException ioe){
String errorMessage = "Error while getting temporary file from external storage";
Log.w(PhotoPickerUtil.class.getCanonicalName(), errorMessage);
return false;
}
}
private static void populateCropExtras(Activity activity, Intent cropIntent) throws IOException { {
// set crop properties
cropIntent.putExtra("crop", "true");
// indicate output X and Y
cropIntent.putExtra("outputX", 300);
cropIntent.putExtra("outputY", 300);
// indicate aspect of desired crop
cropIntent.putExtra("aspectX", 1);
cropIntent.putExtra("aspectY", 1);
cropIntent.putExtra("outputFormat", Bitmap.CompressFormat.PNG.toString());
Uri tempUri = Uri.fromFile(getTempFile(activity));
cropIntent.putExtra("output", tempUri);
}
I'm new to Windows Forms, in my project, i need to change the image in the picture box at runtime. I'm able to do that with the help of a timer. The picture just gets changed. Is it possible to do some transitions when image changes, for example fade in, fade out, blur etc.. If possible could some one please let me know how to do it. I searched in net but in vain.Thanks in advance.
Varun
Simply take new code file and paste below code in it
an original answer for the similar question, answer taken from another question
Answer
using System;
using System.Drawing;
using System.Drawing.Imaging;
using System.Windows.Forms;
public class BlendPanel : Panel
{
private Image mImg1;
private Image mImg2;
private float mBlend;
public BlendPanel()
{
SetStyle(ControlStyles.AllPaintingInWmPaint | ControlStyles.UserPaint | ControlStyles.OptimizedDoubleBuffer, true);
}
public Image Image1
{
get { return mImg1; }
set { mImg1 = value; Invalidate(); }
}
public Image Image2
{
get { return mImg2; }
set { mImg2 = value; Invalidate(); }
}
public float Blend
{
get { return mBlend; }
set { mBlend = value; Invalidate(); }
}
protected override void OnPaint(PaintEventArgs e)
{
if (mImg1 == null || mImg2 == null)
e.Graphics.FillRectangle(new SolidBrush(this.BackColor), new Rectangle(0, 0, this.Width, this.Height));
else
{
Rectangle rc = new Rectangle(0, 0, this.Width, this.Height);
ColorMatrix cm = new ColorMatrix();
ImageAttributes ia = new ImageAttributes();
cm.Matrix33 = mBlend;
ia.SetColorMatrix(cm);
e.Graphics.DrawImage(mImg2, rc, 0, 0, mImg2.Width, mImg2.Height, GraphicsUnit.Pixel, ia);
cm.Matrix33 = 1F - mBlend;
ia.SetColorMatrix(cm);
e.Graphics.DrawImage(mImg1, rc, 0, 0, mImg1.Width, mImg1.Height, GraphicsUnit.Pixel, ia);
}
base.OnPaint(e);
}
}
Build your project. You can now drop a BlendPanel from the top of the toolbox onto your form. Here's a sample program that uses it:
private float mBlend;
private int mDir = 1;
public int count = 0;
public Bitmap[] pictures;
public void myPhoto()
{
pictures = new Bitmap[9];
pictures[0] = new Bitmap(#"Library Images\cf3.jpg");
pictures[1] = new Bitmap(#"Library Images\cf4.jpg");
pictures[2] = new Bitmap(#"Library Images\l1.JPG");
pictures[3] = new Bitmap(#"Library Images\l2.JPG");
pictures[4] = new Bitmap(#"Library Images\l3.JPG");
pictures[5] = new Bitmap(#"Library Images\l4.JPG");
pictures[6] = new Bitmap(#"Library Images\l5.JPG");
pictures[7] = new Bitmap(#"Library Images\l6.JPG");
pictures[8] = new Bitmap(#"Library Images\l7.JPG");
timer1.Interval = 50; //time of transition
timer1.Tick += BlendTick;
try
{
blendPanel1.Image1 = pictures[count];
blendPanel1.Image2 = pictures[++count];
}
catch
{
}
timer1.Enabled = true;
}
private void BlendTick(object sender, EventArgs e)
{
mBlend += mDir * 0.02F;
if (mBlend > 1)
{
mBlend = 0.0F;
if ((count + 1) < pictures.Length)
{
blendPanel1.Image1 = pictures[count];
blendPanel1.Image2 = pictures[++count];
}
else
{
blendPanel1.Image1 = pictures[count];
blendPanel1.Image2 = pictures[0];
count = 0;
}
}
blendPanel1.Blend = mBlend;
}
You'll need to modify the new Bitmap(#"yourimagePath"); calls. Build and run. You should see the displayed image smoothly morph from your first image to your second image without any flickering.
I hope it helps for other...
There is no built-in support for such effects, but you can implement them. I'd suggest to write a custom control that renders the image and have a method for fade-swap, fade itself can be reached with alpha-blending drawing with .NET Graphics class.
However, Graphics class isn't very fast, I don't recommend to use this technique for big images. If you need some fancy UI with hw-accelerated effects, take a look at WPF.
Blend effects are easy to get going by using the ColorMatrix class. There's a good example available in my answer in this thread.
A simple way to get a blur is to resize the image, making it smaller, then redraw it back, making it larger. The Graphics.InterpolationMode property affects the type of blur you'll get.
Those are quicky do-it-yourself solutions. Any decent graphics library has these kind of operations built-in. You probably want something free, check out ImageMagick.NET
To put it simply, not without external (3rd-party) libraries.