I have a couple of TJvImage components on my main form. One is loaded at design time from a partially transparent PNG file. The other is smaller than the first and in front of it. It is loaded at runtime with another partially transparent PNG file.
JvImage1.Picture.LoadFromFile ('Logo.png') ;
JvImage1.Transparent is set to TRUE. The problem is simple: the smaller image is rendered ignoring the alpha channel - i.e. it punches out the background image.
This does not occur when I load both images at design-time. They both show as partially transparent on the form, and display correctly when I run the program.
The real dilemma is that a minimal test program written to try to demonstrate the problem does not show the problem, but the same code in the application proper doesn't behave.
Is there anything about the underlying main form that could affect the behaviour?
I don't know if this is the same for TJvImage but when you set Transparent property of TImage to True it causes TImage to skip rendering any pixel with TransparentColor.
If no transparent color is set the color of lower left pixel is used.
When in such mode TImage doesen't take into accound alpha channel. Infact Transparency only works when you load TBitmap typed image into TImage.
I gues that TJvImage probably works in similar way. So in order to show your image properly you should set the Transparent property to False. This will probably alow TJvImage to render your picture by using Alpha transparency that is encoded to the picture itself.
Related
I have PNG icons for my Delphi XE3 application toolbar that, when added to a TActionToolbar via a TImageList, the alpha channel renders darker than it should, causing the icons to look bad. I think the issue has to do with the TImageList and not something specifically with the TActionToolbar.
Photoshop mockup:
Actual look after importing to TActionToolbar (alpha is darker blue for the folder fill):
Here are my Delphi Object Inspector settings for the TImageList (no, the issue is not the BlendColor property):
Is there a way to get Delphi/Windows/whoever the culprit is to render the alpha channel properly? An option is to make the icons all bitmaps, but I'd rather not go through the headache of editing bitmaps with a transparent color because, well, I'd rather not revert to the days of the dinosaurs... TIA.
The best way I found to deal with this is to paint the background color of your Delphi toolbar (or whatever UI element) underneath every pixel that contains transparency in Photoshop before saving the PNG image. This way, the toolbar icons are totally opaque except for the 100% transparent pixels, so there is no alpha blending that takes place--and hence no ugliness.
Use RRUZ's code here to make the disabled toolbar icons look better.
i wonder, how i could figure out if an image has a transparency effect applied. Is there any way in JavaScript or HTML5? I have a Base64-coded image. Is there a way to read out the transparency-information (alpha-channel). For example, if i load a PNG-Image, then convert it to base64, then drop it to html5-canvas, now how can i know if this has transparency-effect activated?
thanx alot
okyo
When you say 'drop it to html5-canvas', I assume you mean using an image element with the 'data:' URI scheme. Also, let's take it as given that you don't want to write javascript code to parse the image files.
You could do something like this pseudo-code:
create 2 off-screen canvases
color one opaque white and the other opaque black
draw the image on both of them
call getImageData on each canvas, using the image bounds
compare the image data
If the image has any transparent or partially-transparent pixels, then presumably the two canvases will end up at least a little different. One exception would be if the image has the transparency feature enabled but is entirely opaque anyway. Another would be if the non-opaque pixels are only very slightly transparent - not enough to alter a white or black background. But this technique would catch images where transparency is noticeable.
How to get a TPicture from a TImageList?
I need to do Image1.Picture:=...TPicture from an image list, to load an image into a TImage.
An image list stores all my PNG images that are transparent.
I tried to use a bitmap (GetBitmap), but what I need is transparency. Unfortunatelly, I have a white background using a bitmap.
Thanks!
The regular TImageList uses bitmaps. Although they can be partially transparent, it is actually just a fake. In Delphi you can draw bitmaps to be transparent by assigning them a single transparent color. That exact color will be drawn a 100% transparent, while the other colors are not. Usually the color is taken from the bottom left corner of the image.
TPicture itself doesn't do anything. It is merely a container for TGraphic descendants. You'll have to find a type of image that can be transparent.
A convenient format is PNG. PNG event supports an alpha channel, which means that every pixel can be assigned a different transparency value.
Fortunately there are TPngImageLists that combine the ease of TImageList with the power of PNG. You can read this article. It is in Dutch, but maybe Google Translate can help you. Or maybe you can find an english resource on this subject. I've used this imagelist and it's great, because you can have actual icons with an alpha channel and still use them with regular toolbars and speedbuttons.
I'm using Delphi 2006. I have a few PNG images with transparencies and I have to create a GUI using them (top bar, left panel...). The images have different aligns properties. One of the images is the background of the form. The problem here is that I can't align it as alClient because it only occupies the rectangular zone that the other images have left, showing the naked canvas in their transparent zones. What I need is that the background image is put behind all the other images and taking all the canvas size.
Is there anyway to do this? I know I can do this writting some logic in the OnResize event of the form but I was just curious if I was missing something.
Thanks.
Put a TImage on the form and align it with "alClient". Then put an "alClient" aligned Panel on the form. The TPanel is transparent when themes are enabled and "ParentBackground" property is set. Then put the images on the panel and align them at will. If when themes are not enabled is important, you can use a "TJvPanel" which is part of the JVCL library. A search on google also seems to reveal some code for transparent panels.
The above will not help transparency with the "png"s though. AFAIK png support (transparency) is added with D2009 and I don't know if this support includes TImage.
edit: Actually it appears that I owe the very capability to load png images to TImage to the JVCL library itself, and it seems to support transparent "png"s with TImage just fine.
I have a PNG image that uses transparency (it is actually a circle with gradient effect from black in the middle, to transparent on the margins). I am putting this on a form using TImage. I set TForm1.Color and the TForm1.TransparentColorValue to the same value and TForm1.TransparentColor:=true.
Now, when I run the program the gradient part of the image is displayed with the color of the form. What I am looking for is to enable the transparency of the PNG image using the transparent form effect.
What am I doing wrong?
I am using Delphi 2010 Trial.
I suspect you're trying to create something like a transparent splashscreen, if that's the case, you can read these great articles, they describes a nice way to use a transparent png in a delphi form.
Alpha Blended Splash Screen in Delphi - Part 1
Alpha Blended Splash Screen in Delphi - Part 2
Bye.
Your settings are wrong. I am doing this (With a bitmap).
The TImage.Transparent should be false.
The Form.TransparentColourValue should be the colour of the part of The TImage that you want to be transparent.
The Form.TransparentColor should be True.
[Edit]
It does not matter what colour the form is if the Image covers it completely