1 bit depth BMP created with ImageMagick all black using GxEPD2

[rlightner]

I've got a BMP (attached) that was generated with ImageMagick from a color png. the BMP displays just find using any app.

Infranview says colors are: 2   (1 BitsPerPixel) (BW)
Gimp says Color Space: Indexed color (2 colors)

I'm using the drawBitmapFromSpiffs function from

https://github.com/ZinggJM/GxEPD2/blob/master/examples/GxEPD2_Spiffs_Example/GxEPD2_Spiffs_Example.ino

and it just draws the screen a solid black. Am I doing something wrong here?

Thanks in advance!

[ZinggJM]

Please report what processor you use.

Your issue may be related to this post.

I may find time to check this.

You could also have posted diagnostic output from the example.

[rlightner]

TTGO T5 V2.1 ESP32 2.7

https://github.com/lewisxhe/TTGO-EPaper-Series

bmp sig: 19778
File size: 6482
Creator Bytes: 0
Image Offset: 146
Header size: 124
Bit Depth: 1
Image size: 176x264

[ZinggJM]

I see neither a success message nor a failure message in your post, should see: loaded in …

Before I spend time on setting up for test:

Do the other example bitmaps render correctly?

Could it be that your bmp has no palette? the code expects a palette with black and white entry also for b/w.

[david_prentice]

The "output5.bmp" is a regular BMP format file.   176x264  1BPP  i.e. 1-bit colour (monochrome).
It contains its own colour Palette.   You can edit the Palette in IrfanView.   Currently Index:0=WHITE, 1=BLACK

Most BMP programs on Arduino only render 24-bit colour BMP files.

I provide an example that will render BMP files with 1BPP, 4BPP, 8BPP, 16BPP, 24BPP

Although your image is only 1 bit deep,  the individual Palette colours can be chosen from a 16M Colour Palette (24-bits).
Obviously how accurate the colours are on your TFT depend on the TFT resolution (16-bits or 18-bits)

David.

OOPS.  I was replying to a TFT colour display question.   When you are using a monochrome display.
Since your EPaper device can only render BLACK or WHITE it will ignore most of the 24-bits in a Palette Entry.

Edit.  I looked at the drawBitmapFromSpiffs() function from #0
It seems to support all the same BMP formats that I do.
It understands Palettes.   It should display BLACK and WHITE properly.

[ZinggJM]

@David,

How did you check the palette of this picture?

or is this wrong:

Code: [Select]

         file.seekSet(54); //palette is always @ 54


@rlightner,

the palette looks wrong, index 0 and 1 have 2 different colors, but neither black nor white:

palette values below are red green blue

Code: [Select]

Loading image 'betty_4.bmp'
File size: 26326
Image Offset: 118
Header size: 40
Bit Depth: 4
Image size: 204x252
0 0 0
128 0 0
0 128 0
128 128 0
0 0 128
128 0 128
0 128 128
128 128 128
192 192 192
255 0 0
0 255 0
255 255 0
0 0 255
255 0 255
0 255 255
255 255 255
_PowerOn : 36727
_Update_Full : 1527816
loaded in 2842 ms
_Update_Full : 1527948

Loading image 'bb4.bmp'
File size: 206
Image Offset: 62
Header size: 40
Bit Depth: 1
Image size: 34x18
0 0 0
255 255 255
_Update_Part : 556839
loaded in 899 ms
_Update_Full : 1528333

Loading image 'output5.bmp'
File size: 6466
Image Offset: 130
Header size: 108
Bit Depth: 1
Image size: 176x264
255 0 0
0 255 0
_Update_Part : 555762
loaded in 1590 ms
_Update_Full : 1528561
GxEPD2_SD_Example done


Jean-Marc

BTW: thanks to David:

Code: [Select]

// BMP handling code extracts taken from: https://github.com/prenticedavid/MCUFRIEND_kbv/tree/master/examples/showBMP_kbv_Uno



[david_prentice]

The header size is always 54.
If there is a Palette,  it follows the Header.

From IrfanView:  output5.bmp has Palette 255:255:255 , 000:000:000  i.e. WHITE,BLACK

I have some x1 bitmaps e.g. truck.bmp

betty_4.bmp is a 4BPP image i.e. 16 colours.

You should be able to examine the Palette in IrfanView.
Likewise,  you can take a 24BPP colour JPG, PNG, BMP and reduce it to 8BPP (256 colours) quite well.

Reducing to 4BPP or 1BPP requires a bit of skill.    IrfanView does a pretty good job but 1BPP is very difficult to get the "best" look.

I suggest that you look very carefully at your Palette.   I would calculate the Palette once.    Then you render each pixel directly from the Palette.

David.

[rlightner]

I'm using ImageMagick to created the bmp:


convert output.png -filter point -resize "176x264>" -dither FloydSteinberg -define dither:diffusion-amount=85% -monochrome -depth 1 output5.bmp


I'm going to read back over the messages above and try and figure out what I'm doing wrong.


Thanks again for the effort.

[ZinggJM]

@David,

I just added one line of diagnostic output, to try to analyze:

Code: [Select]

       if (depth == 1) with_color = false;
        if (depth <= 8)
        {
          if (depth < 8) bitmask >>= depth;
          file.seekSet(54); //palette is always @ 54
          for (uint16_t pn = 0; pn < (1 << depth); pn++)
          {
            blue  = file.read();
            green = file.read();
            red   = file.read();
            file.read();
            Serial.print(red); Serial.print(" "); Serial.print(green); Serial.print(" "); Serial.println(blue);
            whitish = with_color ? ((red > 0x80) && (green > 0x80) && (blue > 0x80)) : ((red + green + blue) > 3 * 0x80); // whitish
            colored = (red > 0xF0) || ((green > 0xF0) && (blue > 0xF0)); // reddish or yellowish?
            if (0 == pn % 8) mono_palette_buffer[pn / 8] = 0;
            mono_palette_buffer[pn / 8] |= whitish << pn % 8;
            if (0 == pn % 8) color_palette_buffer[pn / 8] = 0;
            color_palette_buffer[pn / 8] |= colored << pn % 8;
          }
        }


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?

Same values in IrfanView HEX view.

[david_prentice]

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.

[david_prentice]

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

Code: [Select]


// 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"

Code: [Select]


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 *..*


Code: [Select]


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)

[ZinggJM]

@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

[rlightner]

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!

[david_prentice]

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.

Code: [Select]



        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.

[ZinggJM]

@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