Trying to scale down a JPEG

Depends on what is limiting the resolution.  You need to figure the pixels per inch at the actual print size.  Your photo editor should give you the number of pixels wide and high.  Divide this by the physical width and height you wish to print the final decal at. It should ideally be about 300 ppi, but 200 will do in a pinch.  Anything less than that will be a poor image regardless of the paper you print it on.

What software are you using, BTW?

I'm using Corel Paintshop Pro 6.

Not sure about paint shop but photoshop has the option to scale an image's physical size leaving the dpi the same and/or reducing the size and increasing the dpi at the same time.  See if paint shop has the latter option.  Does the print settings for that app or your printer allow for different quality print settings?  Make sure they are set to the max.  

JMorgan

I'm using Corel Paintshop Pro 6.

JPG/JPEG compression is horrible, because it was designed to remove detail in images that the human eye won't detect.  Great for photos, horrible for line art and graphics like tail art or lettering decals.  For lossless compression, use GIF or PNG (I prefer the latter, its great for line art and "comic book style" art).

Is this artwork that you created yourself?  The cleanest format to save in, for scaling, is SVG (scalable vector graphics), as it loses no clarity at any size because it is not made of pixels.  Can you convert your image, or export/save your artwork as SVG and give it a try?

I also use PSP 6.  The resize function in the "Image" menu is excellent in that program. It allows you to resize by physical length in either inches or cm (your choice), by the number of pixels, and by pixel density.

I suggest to minimize math to resize by physical size.  Once you have it typed in, peek at the pixels per inch value.  If it is less than 200 pixels per inch you need to get more resolution.  There are two options.

First, if it is only off by a little, you can elect to resample.  This is a little harder than plain resizing, but can save artwork that is off only by a little.

Second, you can resample by a larger value, and then create another, blank layer.  You then create a new piece of artwork, tracing over the original.  This works fine if the design is simple- letters and numbers and simple designs.  The original layer will not show though the second layer, so does not need to be deleted when you complete the artwork on the new layer.

However, redoing the artwork is still a lot of work and you might try to search the i'net for a higher resolution graphic to replace your low res one.

You're correct. Getting a different format file (PNG)  resulted in much better printing!

Thank you!

BlackRook

JPG/JPEG compression is horrible, because it was designed to remove detail in images that the human eye won't detect.  Great for photos, horrible for line art and graphics like tail art or lettering decals.  For lossless compression, use GIF or PNG (I prefer the latter, its great for line art and "comic book style" art).

Is this artwork that you created yourself?  The cleanest format to save in, for scaling, is SVG (scalable vector graphics), as it loses no clarity at any size because it is not made of pixels.  Can you convert your image, or export/save your artwork as SVG and give it a try?

 

HELLO BLACK ROOK

Image compression technologies not only reduce the quantity of data that is stored, but they also keep the output image quality as high as possible while doing so. In the research that has been proposed, we examine a method for image compression that makes use of a unique two-stage image encoding method that makes use of various compression algorithms and wavelet transform methods. This method combines two different kinds of efficient compression algorithms that give more ability to compress image data. 

You can try JPEG Compressor 

Finding the optimal compromise between a high compression ratio and favourable results for visual perception poses a difficult problem for the algorithms that compress images.

I have always used JPEG for decals- never had a problem.  Only real problem with JPEG is subtle shading.  Most decals do not have such shading.  Only ones that do are my wood decals.  I find the softening tool usually fixes that.

Like Don, I use JPEGs all the time with no problem. But since I generally use MS Paint for my image work, I reduce images by 'hand,' i.e., by pasting the image into a document, and dragging the corners to reduce it to the needed size, then printing the document as a decal. This method has always given me surprisingly clear results, even in tiny sizes (like individual gauges in 1/72 scale).

Maybe I should detail how I do the resize.  The resize function in PSP can change the resolution as well as the physical size.  If there are too little pixels to do a resize with acceptible resolution, I do a resolution change as well as a physical  resize.  One can change the resolution (pixels per inch).  If you are increasing the number of pixels, you are given the choice of several interpolation algorithms.  The default is a bicubic interpolation.  I find this generally works well.

Something else- the high quality setting on jpeg compression does not change the pixels per inch.  You end up with the same number of pixels.  Most of the compression is in number of colors.  This can cause banding and stripes  However, this is most evident in full tone images.  Most decals are not of full toned images.  I have run across a few that are.  I use one of several "smoothing" functions.  If there are only several colors, with no shading in each, you do not loose quality in a "high" quality compression.