1 bit depth BMP created with ImageMagick all black using GxEPD2

My apologies. I copied output5.bmp to an SD. Then displayed via an ESP8266.

It shows as Yellow graphics on a Red background.

I will check my algorithm.

I changed the Palette in IrfanView to give Blue graphics on a Cyan background. This renders fine.

I will have to compare the file contents. But this will be later this afternoon.

Why don't I get 255 255 255 and 0 0 0, as I would expect from info of IrfanView? but 255 0 0 and 0 255 0 instead?

Ah-ha. My display must be GREEN graphics on Red background. Not Yellow. So the algorithm is correct. I must see why IrfanView is different to ImageMagick.

David.

Yes, the formats are different: output6.bmp was generated by IrfanView Blue/Cyan

// file:output5.bmp ID  4D42
// size 6466
// offset       130
// width        176
// height       264
// planes       1
// depth        1
// compression  0
// pixelsize    6336
// colorsused   2
// colorsimportant      2

// file:output6.bmp ID  4D42
// size 6398
// offset       62
// width        176
// height       264
// planes       1
// depth        1
// compression  0
// pixelsize    6336
// colorsused   2

Note that ImageMagick generated output5.bmp has an extra "colorsimportant" field. The actual bitmap rendered correctly from the respective "offset"

filespec: output5.bmp
000000 42 4D 42 19 00 00 00 00 00 00 82 00 00 00 6C 00 *BMB...........l.*
000010 00 00 B0 00 00 00 08 01 00 00 01 00 01 00 00 00 *..░.............*
000020 00 00 C0 18 00 00 00 00 00 00 00 00 00 00 02 00 *..└.............*
000030 00 00 02 00 00 00 00 00 FF 00 00 FF 00 00 FF 00 *................*
000040 00 00 00 00 00 FF 42 47 52 73 00 00 00 00 00 00 *......BGRs......*
000050 00 00 00 00 00 40 00 00 00 00 00 00 00 00 00 00 *.....@..........*
000060 00 40 00 00 00 00 00 00 00 00 00 00 00 40 00 00 *.@...........@..*
000070 00 00 00 00 00 00 00 00 00 00 FF FF FF 00 00 00 *................*
000080 00 00 *..*
filespec: output6.bmp
000000 42 4D FE 18 00 00 00 00 00 00 3E 00 00 00 28 00 *BM■.......>...(.*
000010 00 00 B0 00 00 00 08 01 00 00 01 00 01 00 00 00 *..░.............*
000020 00 00 C0 18 00 00 00 00 00 00 00 00 00 00 02 00 *..└.............*
000030 00 00 00 00 00 00 FF FF 00 00 FF 00 00 00 *..............*

You can see the colorsimportant field at offset 0x0032 means that the Palette uses a different format. i.e. Palette is @ 0x007A [FF FF FF 00] [00 00 00 00] White-Black The IrfanView Palette is @ 0x0036 [FF FF 00 00] [FF 00 00 00] Cyan-Blue

Here is a Wikipedia article that describes the BMP file format

I suspect that ImageMagick can generate both formats. I wonder whether it is worth the effort to support the extra

An OS/2 2.x OS22XBITMAPHEADER (BITMAPINFOHEADER2 in IBM's documentation) contains 24 additional bytes

David.

p.s. I have just been listening to an excellent play on the Radio about Nikolai Gogol (my hero)

@David,

yes, I once had a look at that Wikipedia article, and decided it is too complicated for my practical use, and I stay with code that is widely used for Arduino libraries, e.g. the one I found in your library.

Do you have a practical suggestion how to deal with this for users of our libraries?

I downloaded ImageMagick, but I still need some time to learn how to use it.

Users like @rlightner and others could profit from a workaround.

Thank you.

Jean-Marc

The reason why I'm doing it the way I am is that the file encoded this way is only 7 kb, but with the other way, comes out to around 138 kb. I'm trying to minimize the sending over the wire to the device. If at the end of the day I just need to take the hit, I will.

I do appreciate all the work you guys have given to the community. It's a great building block for others to create upon!

You can see the colorsimportant field at offset 0x0032 means that the Palette uses a different format. i.e. Palette is @ 0x007A [FF FF FF 00] [00 00 00 00] White-Black The IrfanView Palette is @ 0x0036 [FF FF 00 00] [FF 00 00 00] Cyan-Blue

So you just have to read 0x32 and if 2 you seek to 0x007A instead of 0x0036 It should not be more than two lines. e.g.

        if (bmpDepth <= PALETTEDEPTH) {   // these modes have separate palette
            bmpFile.seek(50); //colorsimportant
            bmpFile.seek(read32() ? 122 : 54); //important or regular palette

If there are ImageMagick users out there, please could you try creating BMP with different colour depths. IrfanView recognises the colorsimportant field but does not seem to generate it.

I will post the patch on the BMP examples on the MCUFRIEND_kbv Beta.

David.

@David, thank you, now I see it clearly enough; my brain was a bit tired, it seems.

@rlightner,

I will do the change tomorrow morning after a quick test, and put it on GitHub without creating a new version for now.

Jean-Marc

I have posted the change on GitHub e.g. https://github.com/prenticedavid/MCUFRIEND_kbv/tree/master/examples/showBMP_kbv_Uno

@rlightner, you can edit the drawBitmapFromSpiffs() function in the sketch:

        if (depth <= 8)
        {
          if (depth < 8) bitmask >>= depth;
          //file.seek(54); //palette is always @ 54
            file.seek(50); //colorsimportant
            file.seek(read32() ? 122 : 54); //important or regular palette

Please test your existing file.

If all works ok, I would appreciate it if you go back to ImageMagick See if you can start with a colour JPG and reduce colours to 256-colour, 16-colour, 2-colour BMP files.

It would be nice if you posted the result. e.g. attach the files in a ZIP

David.

Will do!

I have just installed ImageMagick on this Win10-64 PC

I am lost. I can't even find how to set a Path to the program or even send a simple command

 "C:\Program Files\ImageMagick-7.0.8-Q16\magick.exe" tractor10.jpg -colors 256 tractor_8.bmp

I just get Parser errors.

David.

Should have put it under your "Program Files" directory if you installed the 64 bit version.

I just downloaded the Windows installer. I assume that it knows where it wants to store stuff.

IrfanView calls itself "v4.41 64-bit" but installed itself in "/Program Files" and not "/Program Files (x86)"

David.

Correct, if your OS is 64bit, 64bit apps get installed in "/Program Files" and 32bit go in the "/Program Files (x86)" folder.

Woo-Hoo. This Win10 PC defaults to PowerShell which is horrible. I found cmd.exe and everything works nicely.

I have created some BMP files with different color depth. I get different values in the colorsimportant field e.g. 2, 16, 256

But the result is horrible.

I have a lot of learning to do.

IrfanView tends to do this stuff for you e.g. if you ask it to reduce to 16 colours it makes the "best possible" Palette and the end result looks good.

David.

I'm executing this via a function in firebase, which has 'convert' available to the environment, so its not something I can do by hand.

this is the line that gets executed:

convert **from_filename.png** -filter point -resize "176x264>" -dither FloydSteinberg -define dither:diffusion-amount=85% -monochrome -colors 2 **output_filename.bmp**

I have made a safer calculation for MCUFRIEND_kbv examples:

        if (bmpDepth <= PALETTEDEPTH) {   // these modes have separate palette
            bmpFile.seek(bmpImageoffset - (4<<bmpDepth)); //54 for regular, diff for colorsimportant
            bitmask = 0xFF;

your edit would be:

        if (depth <= 8)
        {
          if (depth < 8) bitmask >>= depth;
            file.seek(imageOffset - (4<<depth)); //54 for regular, diff for colorsimportant
          //file.seek(54); //palette is always @ 54

Thanks for your sample command. I am struggling with ImageMagick.
I have created tractor_1.bmp tractor_4.bmp tractor_8.bmp with ImageMagick
and created tractor_11.bmp tractor_44.bmp tractor_88.bmp with IrfanView

ImageMagick creates bigger headers on all 3 files. And creates a RLE bitmap for the 256-colour file.
My programs reject the RLE flag as an unsupported format.

I have attached a ZIP.

David.

Edit. Added output6.bmp to ZIP. This was generated by Irfanview with Blue graphics and Cyan background.
Jean-Marc’s program should distinguish between the two colours i.e. Cyan->WHITE and Blue->BLACK

magick tractor10.jpg -depth 1 -colors 2 tractor_1.bmp
magick tractor10.jpg -depth 4 -colors 16 tractor_4.bmp
magick tractor10.jpg -depth 8 -colors 256 tractor_8.bmp

tractors.zip (76.2 KB)

What command are you using with imagemagick to create them?

Using the simple command produced rubbish BMP files.
Most importantly the 256-colour BMP defaults to using RLE8 compression (which I don’t support)
Not only does it produce RLE8 but the RLE8 files are bigger than uncompressed files!

I have improved my ImageMagick commands e.g.

magick convert tractor10.jpg -compress none -type palette -dither FloydSteinberg -colors 256 -depth 8 tractor_8.bmp

magick convert marilyn-monroe-9412123-1-402.jpg -resize 20% -compress none -type palette -dither FloydSteinberg -colors 2 -depth 1 marilyn_1.bmp

My original tractor JPEG is 276x182. I do not change the size
My original Marilyn JPEG is 1200x1200. I resize it to 240x240

If anything, ImageMagick seems to produce a slightly better monochrome than IrfanView.

Although there is a lot to learn, the command line ImageMagick is much more powerful than a GUI.

I don’t know whether you own a colour TFT e.g. to view all the BMP in colour.
I would like to know whether Jean-Marc’s sketch displays them on EPaper and how effectively.

You can obviously view the BMP files on the PC to see what they should look like.
256-colour Palette is very good.
16-colour Palette is surprisingly good.
2-colour Palette is as good as you can expect.

David.

bitmaps2.zip (187 KB)

Version 1.2.2 of my library GxEPD2 is available.

  • fixed BMP handling, e.g. for BMPs created by ImageMagick

@rlightner, @david_prentice, thank you for your contributions.

Jean-Marc

@Jean-Marc,

What is your opinion of color BMP rendered on a monochrome EPaper ?

If I build a monochrome Palette e.g.

            for (col = 0; col < n; col++) {
                pos = read32(bmpFile);    //map palette to 5-6-5
                uint8_t r = (pos & 0xFF0000) >> 16;
                uint8_t g = (pos & 0x00FF00) >> 8;
                uint8_t b = (pos & 0x0000FF) >> 0;
                palette[col] = (r + g + b < 0x0180) ? 0x0000 : 0xFFFF;  //monochrome
                //palette[col] = tft.color565(r, g, b);  //regular color
                //palette[col] = ((pos & 0x0000F8) >> 3) | ((pos & 0x00FC00) >> 5) | ((pos & 0xF80000) >> 8);
            }

The 16-color and 256-color BMPs look a bit bleached. Adjusting the 0x0180 threshold helps but is not as good as ImageMagick or IrfanView.

I presume that EPaper users will often want to create good monochrome.

Incidentally, a 16-Grayscale OLED looks pretty good. Much like my surprise with 16-color BMP.

David.

@David

What is your opinion of color BMP rendered on a monochrome EPaper ?

It is in any case a (bad) compromise. And it is even worse with 3-color e-paper, b/w/r or b/w/y.

I think it is preferable to have the user generate and adjust a b/w or 3-color BMP for his purpose.

But my BMP examples just should be able to render any BMP bitmap. I didn't experiment with thresholds, and the code may even be wrong, at least earlier versions were.

I didn't pay much attention testing your tractor bitmaps so far, they looked more or less the same. Maybe I take a second look tomorrow, and also at your bitmaps2, and on b/w/r e-paper.

Maybe I should mention that some SPI b/w e-paper displays can be used to show 4 grey levels, using a special waveform table and the fact that the "previous" and "new" buffer provide 2 bits per pixel, normally used for differential update. Parallel IF e-paper displays usually have 16 grey levels.

Jean-Marc