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Why Do Flattened Images Require So Much Space?

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I was just playing around and inserted 5 .png images with transparent backgrounds onto an 800 x 600 canvas in PDN. Each image was roughly 200 Kb and when I flattened them, the file was nearly 1000 Kb. Can somebody please explain why the file size didn't decrease when I flattened the image?

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I was just playing around and inserted 5 .png images with transparent backgrounds onto an 800 x 600 canvas in PDN. Each image was roughly 200 Kb and when I flattened them, the file was nearly 1000 Kb. Can somebody please explain why the file size didn't decrease when I flattened the image?

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why the file size didn't decrease when I flattened the image?

Why did you think it will?

Because each image has its own Alpha channel (The transparent layer). When the images are expanded, there are 5 transparent layers, but when they are flattened, there is only one. At least that's how I'm thinking it works. Assuming that I am right, 1 Alpha layer shouldn't require as much space as 5 Alpha layers.

Or does flattening the images still leave an Alpha layer in between each image? If so, that would explain why the file size didn't decrease.

I posted the question because I am hoping to get a better understanding of how Alpha layers work and I thought somebody here might have an answer. ;)

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why the file size didn't decrease when I flattened the image?

Why did you think it will?

Because each image has its own Alpha channel (The transparent layer). When the images are expanded, there are 5 transparent layers, but when they are flattened, there is only one. At least that's how I'm thinking it works. Assuming that I am right, 1 Alpha layer shouldn't require as much space as 5 Alpha layers.

Or does flattening the images still leave an Alpha layer in between each image? If so, that would explain why the file size didn't decrease.

I posted the question because I am hoping to get a better understanding of how Alpha layers work and I thought somebody here might have an answer. ;)

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The transparent areas are all "zeros" and compress out to almost nothing. Storage requirements are not proportional to the number of pixels in all layers. They are proportional to the "complexity" of the layers. With 5 layers and lots of transparency you have "5 simple layers," each one having large regions of easily compressible pixel data. Flattened, you now have "1 complex layer" with no easily compressible areas.

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The transparent areas are all "zeros" and compress out to almost nothing. Storage requirements are not proportional to the number of pixels in all layers. They are proportional to the "complexity" of the layers. With 5 layers and lots of transparency you have "5 simple layers," each one having large regions of easily compressible pixel data. Flattened, you now have "1 complex layer" with no easily compressible areas.

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