如何在 windows tasm dosbox 中读取图像文件并在屏幕上显示 [英] How to read image file and display on screen in windows tasm dosbox

问题描述

我目前正在使用 dosbox 在 tasm 中学习图形编程.我一直在使用一堆循环来绘制方形像素块，这真的很难.我想知道是否有办法读取图像并显示它.我知道如何阅读 txt 文件，也许这是一个开始.请帮忙

解决方案

您需要编写/使用图像加载器或使用您自己的图像文件格式.BMP 可能看起来很简单，但其中包含了太多像压缩像素格式等内容，但您仍然可以专注于特定类型的 BMP 而忽略所有其他类型...

回到 MS-DOS 时代，我使用带有调色板的 256 色 PCX 图像，因为我使用了 256 色视频模式.这里NASM LINEZ游戏示例:

• Im currently learning graphical programming in tasm using dosbox. Ive been using a bunch of loops to draw square blocks of pixels and its really hard. I want to know if theres a way to read an image and display it. I know how to read a txt file maybe this is a start. Pls help

  解决方案

  You need to write/use image loader or use your own image file format. BMP may look simple but has too much in it like compression pixel formats etc but you still can focus on a specific type of BMP and ignore all the others...

  Back in the days of MS-DOS I was using 256 color PCX images with palette as I used 256 color video modes. Here NASM LINEZ game example:

  • Color Lines - simple game in C++/the checking algorithm

  see the pcx: subroutine. It decodes loaded PCX file from memory ds:0 to raw VGA image at es:di. Beware it does support just 64 KByte size limit !!! Now to visualize the image you would have to copy es:di content into VideoRAM (assuming A000:0000) for example with rep movsd or you can set es:di to it in the first place (but that could flicker).

  This PCX loader however does not use palette from the image so you need to encode it ... (the routines to change VGA palette are included in the source you just need to extract the RGB values from PCX I think it was at the end of file) Look here:

  • my C++ PCX loader with palette

  if converts PCX to 32bit raw image.

  For more info about MS-DOS game programing see PCGPE 1.0

  Here another game example (TASM) which uses own image file-format:

  • What is the best way to move an object on the screen?

  It has text menues, binary file access, 320x200 sprite graphics, 3 human players

  [Edit1] New code

  I removed the old code example and instead I created compilable and working 8bit PCX with color palette viewer in TASM. It uses VESA 800x600x256 colors mode (103h).

  The image must fit into screen and its file size must be less than 64 KByte !!!

  I did not add any checks or error messages ... It simply loads file image.pcx and displays it on VESA then wait on key hit end exit. Here the TASM source:

  PCX.ASM

  ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
      .386
      IDEAL
      MODEL TINY
  ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
      DATASEG
  file:   db 'image.pcx',0    ;filename to load
  buff:       
  ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
      CODESEG
      STARTUPCODE
  
      scrxs   equ 800
      scrys   equ 600
      mov ax,103h ; VESA 800x600x256
      call    vesamod
      mov al,0
      call    vesapag
  
  ;   scrxs   equ 320
  ;   scrys   equ 200
  ;   mov ax,19   ; VGA 320x200x256
  ;   int 10h
  
      lea dx,[file]   ; load PCX into DS:buff, CX bytes
      call    fopen
      lea dx,[buff]
      mov cx,64000    ; some max value to fit into DS segment
      call    fread       ; CX is PCX real size
      call    fclose
  
      lea si,[buff]   ; decode directly to VRAM
      mov ax,0A000h
      mov es,ax
      mov di,0
      call    pcx
  mainl0:
      mov ax,256  ; test keyboard
      int 16h
      jz  mainl0
      sub ax,ax   ; clear key buffer
      int 16h
  
      mov ax,3    ;|VGA 80x25 text
      int 16
      ret
  ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
  vesamod:pusha               ;set VESA videomode ax
      mov     bx,ax
      mov     ax,4f02h
      int     16
      popa
      ret
  ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
  vesapag:pusha               ;al=page  switch vesa video page window A
      mov [cs:scrpag],al
      mov     dl,al
      sub     dh,dh
      sub     bx,bx
      mov     ax,4f05h    ; window A
      int     16
      popa
      ret
  ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;  .386P
  scrpag  db 0
  ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;  .386P
  hand    dw 0        ;###    handler...
  ferr    db 0        ;###    DOS error code
  ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
  fopen:  pusha       ;DS:DX = file name, [hand] <= file handle
      mov ax,3D02h
      int 21h
      mov bl,0
      jnc fopen0
      mov bl,al
      sub ax,ax
  fopen0: mov [cs:hand],ax
      mov [cs:ferr],bl
      popa
      ret
  ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
  fclose: pusha       ;[hand] = file handle
      mov bx,[cs:hand]
      mov ah,3eh
      int 21h
      mov bl,0
      jnc fclose0
      mov bl,al
      sub ax,ax
  fclose0:mov [cs:ferr],bl
      mov [cs:hand],ax
      popa
      ret
  ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
  fread:  pusha       ;DS:DX = adr, CX = lenght, [hand] = hand, CX => read
      mov bx,[cs:hand]
      mov ah,3Fh
      int 21h
      mov bl,0
      jnc fread0
      mov bl,al
      sub ax,ax
  fread0: mov [cs:ferr],bl
      mov [cs:freadsz],ax
      popa
      mov cx,[cs:freadsz]
      ret
  freadsz dw 0
  ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
  pcx:    pusha           ;decode pcx at ds:si to es:di cx = PCX size
      push    ds
      push    es
      push    ecx
      push    edx
  
      push    si      ;set palette
      add si,cx
      sub si,768
      sub ax,ax   
  pall0:  mov dx,3C8h
      mov al,ah
      out dx,al
      inc dx
      lodsb
      shr al,2
      out dx,al
      lodsb
      shr al,2
      out dx,al
      lodsb
      shr al,2
      out dx,al
      inc ah
      jnz pall0
      pop si
  
      mov ax,[ds:si+8]    ;get xs
      sub ax,[ds:si+4]
      inc ax
      mov [cs:pcxxs],ax
      mov [cs:pcxx],ax
  
      mov ax,[ds:si+10]   ;get ys
      sub ax,[ds:si+6]
      inc ax
      mov [cs:pcxys],ax   
  
      mul [cs:pcxxs]
      push    dx
      push    ax
      pop edx
      add si,128      ;src start after pcx header
      sub ecx,ecx     ;RLE decoder of PCX
  pcxl0:  lodsb
      mov cx,1
      cmp al,192
      jb  pcxr0
      mov cl,al
      and cl,63
      lodsb
  pcxr0:  mov bx,cx
  pcxl1:  call    point
  
      dec [cs:pcxx]   ;correct next screen line position if end of PCX line
      jnz pcxr1   
      mov ax,[cs:pcxxs]
      mov [cs:pcxx],ax
      neg ax
      add ax,scrxs
      add di,ax
      jnc pcxr1
      ; page swith
      mov al,[cs:scrpag]
      inc al
      call    vesapag
  
  pcxr1:  loop    pcxl1
      mov cx,bx
      sub edx,ecx
      jz  pcxesc
      jnc pcxl0
  
  pcxesc: pop edx
      pop ecx
      pop es
      pop ds
      popa
      ret
  pcxxs   dw  0   ;PCX resolution
  pcxys   dw  0
  pcxx    dw  0   ;actual X coordinate 
  ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
  point:  mov [es:di],al      ;point      ;estosb 
      inc di
      jnz pntesc
      ; page swith
      mov al,[cs:scrpag]
      inc al
      call    vesapag
  pntesc: ret
  ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
      END
  ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
  

  So take any image up to 800x600 convert it to 256 color PCX with palette and rename it to image.pcx. Then place it to your *.com file and run. I compiled it with Volcov commander extension script vc.ext like this:

  asm:@c:languagecompil	asm	asm !.! /ic:languagesource	asminc
      @c:languagecompil	asm	link !.obj /t /x
      @del !.obj
  

  so each time I hit the enter on any asm file it will compile. Just change the paths and if you are not targeting *.com files then change the /t switch accordingly. Here preview from my DOSBox:

  这篇关于如何在 windows tasm dosbox 中读取图像文件并在屏幕上显示的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！