resize and transparency got lost

[satellit]

Hi,

1) I want to resize a png from 80x78 to a 60x78 png, non-proportional. The corners of the original are transparent. After resizing I get always a black boarder. I tried several options already even If I had to pick the transparent colour. I attached the png. What am I doing wrong?
2) Is it possible to make a transparent canvas boarder?

I tried the search in advance but I could find an appropriate answer.
Thanks in advance

[Bhikkhu Pesala]

You always get a black border because what you see in IrfanView on opening a transparent PNG is the default Windows colour. Change it to yellow and the border will be yellow. Actually, it's transparent and it will be transparent in Web browsers.

[satellit]

Thanks for the quick answer. Maybe you noticed that your png has a black boarder. You see it already on your attachment. Can one avoid this?

[Mij]

I would have expected your search to have found the post I made only a couple of weeks ago (click here)
Although it is answering a slightly different question, most of what you need to know is there.

Here are the steps you would need
1. MENU: Options > Properties/Settings
2. TAB: Viewing
3. DIALOG: Main window color - change to a less confusing color e.g red > Tick "Show PNG/TIF/TGA/DDS alpha /transparent color > OK
4. MENU: Image > Resize/resample
5. DIALOG: Set New Size (whatever) > Size method "Resize" > OK
6. MENU: File > Save As
7. DIALOG: Save as type - PNG > Tick "Show options dialog" if not already ticked
8. PNG save options DIALOG: Tick "Save transparent color" > Tick "Use main window color for transparency" > Untick "Save Transparency as Alpha channel" > Save

However you already have an Alpha channel saved on the image you posted, probably because you saved it without unticking that option I have underlined above. So the image is going to be slightly transparent all over and will have a reddish tinge to it. Hopefully you still have your original and can now go back and save it correctly.

[Bhikkhu Pesala]

As I said, change the default Window colour, but it makes no difference because the border is transparent when used on web pages.

[Mij]

Sorry. We seem to have got crossed posts discussing different issues.

[satellit]

Thanks for your answer. It works almost.
I get a red boarder (with red background) or I get a white boarder (with white background). The later one is ok however the white in the picture is also transparent. Is there anything which I can improve?

[satellit]

So, I found a solution on Linux with: convert "Das Erste HD_org.png" -scale '60x78!' "Das Erste HD.png"
I attached the result. The complete picture is homogeneously transparent. It would be great, if IrvanView could also support this because I am a real IrvanView fan!
Thanks for your support

[satellit]

The command for a transparent border under Linux is: convert "Das Erste HD.png" -bordercolor none -border 10x0 "Das Erste HD_none.png"
I have attached the picture with the left and right border.

Could you please fix the bug in IrfanView? I would like that these features (resizing transparent png and transparent border) work also under Windows or should I contact Irfan directly?
Thanks a lot!

[Mij]

Thanks for your answer. It works almost.
I get a red boarder (with red background) or I get a white boarder (with white background). The later one is ok however the white in the picture is also transparent. Is there anything which I can improve?

Satellite, that is where the confusion lies. I do not think you have posted the real original image. What you have posted already has transparency which shows up when you have the red main window color which I suggested. I have attached 3 screen captures, all at 100% zoom so that we can see them more clearly. The first is what you posted. It has a pink tinge because it is partially transparent. I saved it again without any transparency and show that as capture 2. That is I think your real original and I can see that it has pure white (255,255,255) corners but also has some other pure white pixels in the picture area and on some edges. If I save this with transparency by clicking on one of the corners to select transparent color, I get what you see in capture 3. The red window color clearly shows where the white pixels are. You can hide these pixels by putting it on a white window background but they will always be apparent over a colored one.

If I want to use transparency to hide a frame around an image I would choose a frame color that I am sure does not occur anywhere else in the image and I would resize the original before I applied the transparency because I do not know exactly what will happen when the application tries to resize a transparent one.